## Practical Weights and Measures Simple Conversions

### Important or relevant information is in red. Metric information is in green.

 Common Metric/English Conversions: 1 inch = 1 inch = 1 foot = 1 yard = 1 mile = 1 meter = 1 kilometer = 1 gram = 1 oz. = 1 lb. = 1 kg. = 1 gal. = 1 liter = 2.54 centimeters (cm.) 25.4 millimeters (mm.) 30.48 centimeters (cm.) 91.44 centimeters (cm.) 1609.4 meters or 1.6 km. 39.37 in. 0.6215 miles or 3281.5 ft. 0.03527 oz. or 15.43 grains 28.3495 grams (g.) 453.59 grams (g.) 2.2046 lb. 3.79 liters 0.264 gal. or 1.057 qt. These Metric conversions are located elsewhere on this page, but are the most commonly needed.

 Length Measurements: 1 mil = 1 inch = 1 inch = 1 inch = 1 hand = 1 wooden 2 X 4 = 1 span = 1 foot (ft.) = 1 foot (ft.) = 1 common cubit = 1 sacred cubit = 1 yard (yd.) = 1 yard (yd.) = 1 pace = 1 meter = 1 rod = 1 fathom = 1 hank = 1 rod (rd.) = 1 stadium (stadia pl.) linear track = 1 furlong = 1 kilometer = 1 mile (mi.) = 1 mile (mi.) = 1 mile (mi.) = 1 mile (mi.) = 1 mile (mi.) = 1 geographical or nautical mile = 1 league = 1 parasang = 1 degree (of Latitude on Meridian = or Longitude on Equator)      15 degrees (Latitude of time zones) = 1 light-year = 1 light-year = 1 parsec = 1/1000th in. or 0.001 in. 3 barleycorns - used by shoemakers 2.54 centimeters (cm.) 25.4 millimeters (mm.) 4 inches - used measuring horses 3 1/2" X 1 1/2" 9 inches 12 inches 30.48 centimeters (cm.) 18 inches - distance from the elbow       to the tip of the middle finger! 21.888 inches       - used measuring arks 3 feet 91.44 centimeters (cm.) 3 feet 39.37 in. 5 paces 6 feet - depths of sea 100 linear feet - of rope 5 1/2 yards 607 ft. (Athens) or 630 ft. (Olympic) 40 rods or 660 ft. 0.6215 miles or 3281.5 ft. 8 furlongs 320 rods 1760 yards 5280 feet 1609.4 meters or 1.6 km. 1.15 statute miles (6080.27 feet) 3 geographical miles 30 stadia (about 3.5 mi.) 60 geographical miles, or       69.16 statute miles 900 miles at equator distance light travels in 1 earth year 5.87 X 10^12 mi. (5.87 trillion mi.) 3.26 light-years 1 mi. = 320 rd. = 1760 yd. = 5280 ft. = 63360 in. 1 Megameter = 1 Myriameter = 1 Kilometer = 1 Hectometer = 1 Dekameter = 1 Meter = 1 Decimeter = 1 Centimeter = 1 Millimeter = 1 Micron = 1,000,000 Meters or 621.37 miles 10,000 Meters or 6.2137 miles 1,000 Meters or 3,280 ft 10 in. 100 Meters or 328 ft 1 in. 10 Meters or 393.7 in. 39.37 in. 1/10 Meter or 3.937 in. 1/100 Meter or 0.3937 in. 1/1000 Meter or 0.03937 in. 1 millionth of a Meter In 1983, a meter was redefined as the length of the path traveled by light in a vacuum during a time interval of 1 / 299,792,458ths of a second. Don't you like that better than just "39 inches"? Surveyor's Length Measurements: 1 link (l.) = 1 rod (rd.) = 1 chain (ch.) = 1 mile (mi.) = 7.92 inches 25 links 4 rods 80 chains 1 mi. = 80 ch. = 320 rd. = 8000 l. = 63360 in. Mariner's Length Measurements: 1 fathom = 1 cable length (or cable) = 1 mile = 1 statute mile = 1 nautical mile = 6 feet 100 fathoms (120 in US Navy) 7 1/2 cable lengths 5280 feet 6080 feet    (see knot)

 Square Measurements (Area): 1 square foot (sq. ft.) = 1 square yard (sq. yd.) = 1 square (used in roofing) = 1 square rod (sq. rd.) = 1 acre (A.) = 1 acre (A.) = 1 square mile (mi.) = 1 township = 144 square inches 9 square feet 100 square feet 30 1/4 square yards 160 square rods 43,560 square feet 640 acres 36 square miles, or       36 sections 1 Hectare = 1 Are = 1 Centare = 10,000 sq. meters or 2.471 acres 100 sq. meters or 119.6 sq. yds. 1 sq. meter or 1550 sq. in.

 Cubic Measurements (Volume): 1 cubic foot (cu. ft.) = 1 cubic yard (cu. yd.) = 1 CCF = 1 MCF = 1 bushel, dry measure = 1 cord (C.) = 1 cord (C.) = 1 cord foot = 1 load = 1728 cubic inches 27 cubic feet 100 cubic feet - volume of nat. gas 1000 cubic feet - vol. of nat. gas 1 1/4 cubic feet 128 cubic feet Wood, stacked 8ft L X 4ft H X 4 ft Wood, stacked 1ft L X 4ft H X 4 ft Dirt, 1 cubic yard 1 cubic Centimeter = 1 cubic Meter = 1 cubic Meter = 0.06102 cubic in. 35.34 cubic ft. 1.3079 cubic yd.

 Liquid Capacity (Volume): 1 Teaspoon (tsp.) = 1 Teaspoon (tsp.) = 1 Tablespoon (tbl.) = 1 Tablespoon (tbl.) = 1 ounce (oz.) = 1 ounce (oz.) = 1 ounce (oz.) = 1 ounce (oz.) = 1 cup of sugar = 1 cup (cp.) = 1 pint (pt.) = 1 pint (pt.) = 1 pint (pt.) = 1 quart (qt.) = 1 liter = 1 liter = 1 gallon (gal.) = 1 gallon (gal.) = 1 gallon (U.S. gal.) = 1 gallon (U.S. gal.) = 1 gallon (Imperial gal.) = 1 barrel (bbl.) liquid = 1 barrel petroleum = 1 hogshead (hhd.) = 1 ccf. = 1 ccf. = 60 drops 1/ 6 fluid oz. or 1/3 fluid dram 1 fluid dram 3 Teaspoons or 1/2 fluid oz. 360 drops 29.6 milliliter (ml.) 6 Teaspoons 2 Tablespoons See Weight & Volume >> 8 ounces (oz.) 2 cups (cp.) 16 ounces (oz.) 4 gills (gi.) 2 pints or 0.946 liters 0.264 gal. or 1.057 qt. 61.022 cu. in. 4 quarts 3.79 liters 231 cu. in. (about 8.34 lbs.) see >> 0.13368 cu. ft. 277.274 cu. in. (about 10 lbs.) 31 1/2 U.S. gallons 42 U.S. gallons 2 barrels 100 cubic feet 748 gallons 1 gal. = 4 qt. = 8 pt. = 16 cp. = 32 gi. = 128 oz. Also see Apothecaries' Liquid Measurements (for medicines) below

 Apothecaries' Liquid Measurements (for medicines) : 1 minim (m) = 1 fluid dram = 1 cubic centimeter (cc) = 1 fluid dram = 1 fluid ounce = 1 pint = 1 gallon = about 1 drop 60 minims (m) 1 milliliter (ml) 1 teaspoon 8 fluid drams 16 fluid ounces 8 pints

 Medical Drug Conversions: 1 ug. (microgram) = 1 ug. = 1 ugRE. (Retinol Equivalent) = 1 mEq. (milliequivalent) = 1 mg. = 1 kg. = 1 mcg. (microgram) * 40 I.U. (International Units) ** 5   I.U. (International Units) 75 mg (milligram) 1 milligram (1/1000 gram) 2.2046 lbs. * Notice ug. and mcg. are both micrograms or 1/1,000,000th of a gram, whereas mg. is a milligram or 1/1,000th of a gram. ** International Units are used here in the context of a specific measurement unit of POTENCY, not weight. Certain vitamins are measured in these units, which are not to be confused with the entire Metric system of values which is also called the 'International System of Units' (SI).

 Metric Capacity (Volume): Kiloliter or Stere - Hectoliter - Dekaliter - Liter - Deciliter - Centiliter - Milliliter - # of liters 1000 100 10 1 1/10 1/100 1/1000 Cubic Measure 1 cu. meter 1/10 cu. m. 1/100 cu. m. 1000 cu. cm. 100 cu. cm. 10 cu. cm. 1 cu. cm. Dry Measure 1.308 cu. yd. 2 bu., 3.35 pks. 610.22 cu. in. 61.022 cu. in. 6.1022 cu. in. 0.6102 cu. in. 0.061 cu. in. Liquid Measure 264.17 gal. 26.417 gal. 2.6417 gal. 0.264 gal. 3.38 fluid oz. 0.338 fluid oz. 0.27 fluid dram The value on every row is 10 times the following row. Notice the conversion between liters and cubic inch - the old GM car engine of the 60s, the 389 cu. in. V8, is really slightly less than 6.4 liters!

 Comparing Liquid and Dry Capacity (Volume): Liquid measure - Dry measure - Cu.In. in 1 Gal. 231 268.8 Cu.In. in 1 Qt. 57.75 67.2 Cu.In. in 1 Pt. 28.875 33.6 Cu.In. in 1 oz. 1.8 2.1

 Dry Capacity (Volume): 1 quart (qt.) = 1 peck (pk.) = 1 bushel (bu.) = 2 pints 8 quarts 4 pecks 1 bushel = 4 pk. = 32 qt. = 64 pt.

 Avoirdupois Weight (Metals, Groceries, etc.): 1 grain (gr.) = 1 gram = 1 dram (dm.) = 1 ounce (oz.) = 1 ounce (oz.) = 1 pound (lb.) = 1 pound (lb.) = 1 kilogram (kg.) = 1 quarter = 1 hundredweight (cwt.) = 1 ton (T.) = 1 ton (T.) = 1 long ton (of coal) = 1 metric ton = wonton = 0.0648 grams * 0.03527 oz. or 15.43 grains 27.34 grains 16 drams 28.3495 grams (g.) 16 ounces 453.59 grams (g.) 2.2046 lb. 25 pounds 100 pounds 20 hundredweight (cwt.) 2000 pounds (& short ton of coal) 2240 pounds 1000 kilograms 1 soup 1 ton = 20 cwt. = 2000 lb. = 32000 oz. * Notice the definition of a grain is the same for all weights, avoirdupois, troy, and apothecaries'. Troy Weight (Precious Metals, Gold, etc.): 1 carat = 1 carat = 1 carat = 1 grain (gr.) = 1 pennyweight (pwt.) = 1 ounce (oz.) = 1 pound (lb.) = 4 'carat' grains 3.168 troy grains (0.2 gram) 100 points 0.0648 grams * 24 grains 20 pennyweights 12 ounces 1 pound = 12 oz. = 240 pennyweights = 5760 grains * Notice the definition of a grain is the same for all weights, avoirdupois, troy, and apothecaries'. Apothecaries' Weight (medicine): 1 grain (gr.) = 1 scruple = 1 dram = 1 ounce (oz.) = 1 ounce (oz.) = 1 pound (lb.) = 0.0648 grams * 20 grains 3 scruples 8 drams 28.3495 grams (G.) 12 ounces (oz.) 1 pound = 12 oz. = 96 drams = 288 scruples = 5760 grains * Notice the definition of a grain is the same for all weights, avoirdupois, troy, and apothecaries'. Obscure Weights: 1 stone = 1 firkin = 1 cental = 1 quintal = 1 keg = 1 barrel = 1 barrel = 1 barrel = 14 pounds 100 pounds (of butter) 100 pounds (of grain or flour) 100 pounds (of dried fish) Yumm! 100 pounds (of nails) 196 pounds (of flour) 200 pounds (of pork or beef) 280 pounds (of salt) Comparison of Weights: 1 pound avoirdupois = 1 ounce avoirdupois = 1 pound troy, or apothecaries = 1 ounce troy, or apothecaries = 7000 grains 437.5 grains 5760 grains 480 grains

 Weight and Volume: 1 gal. of water = 1 cu. ft. of water = 1 liter of water = 1 gal. of gasoline = 1 gal. of Ethanol gasoline = 1 gal. of fuel oil = 1 gal. of Propane = Note: Dry Weight to 1 cup of Sugar (8 oz. volume) = 1 lb. of Sugar = 1 lb. of Butter = 1 lb. of Flour = 1 lb. of Rice = 8.34 lbs. (133.44 oz. av. * )   231 cu. in. 62.4 lbs. (1000 oz. av. * )   7.5 gal. 1 kg. 5.8 - 6.5 lbs. (typically 6.1) ** 6.59 lbs. ** 7.7 lbs. 4.24 lbs. Volume 6.8 oz. (weight) about 2 cups (actually 18.8 fluid oz.) 2 cups 4 cups 4 cups The water is distilled, at its maximum density, with the barometer at 30 in. Water serves as a standard substance for defining units of measure, and it's readily available. * av. = avoirdupois wt. ** Gasoline weight varies based on oxygen content, up to 3% in some mixtures. Ethanol usually has the highest content and is now called Unleaded Premium. Because of the oxygen content, gasoline can be compressed, unlike water. And because gasoline weighs less than water, it floats on top! Any water in your car's fuel tank will settle to the bottom, where the fuel intake is located, so the water gets used first! Gas and water don't mix, they separate, but even worse, Alcohol and water mix very well. So, consider the Ethanol-blended gasolines - the ones containing alcohol -- that alcohol will mix with the water and totally contaminate the entire mixture of gas, alcohol, and water!!

 Metric Weight and Volume: Millier or Ton - Quintal - Myriagram - Kilogram - Hectogram - Dekagram - Gram - Decigram - Centigram - Milligram - Microgram - # of grams 1,000,000 100,000 10,000 1,000 100 10 1 1/10 1/100 1/1000 1/1,000,000 Water * 1 cu. meter 1 hectoliter 10 liters 1 liter 1 deciliter 10 cu. centimeters 1 cu. centimeters 1/10 cu. centimeters 10 cu. millimeters 1 cu. millimeter Avoirdupois Weight 2204.6 lb. 220.46 lb. 22.046 lb. 2.2046 lb. 3.5432 oz. 0.3527 oz. 15.432 grains 1.5432 grains 0.1543 grains 0.0154 grains * = Weight of what quantity water at maximum density. Water serves as a standard substance for defining units of measure.

 Speed (Velocity) Measurements: 1 mile per hour (mph) = = = 1 Knot = The speed of light in air = = The speed of light in a vacuum = The speed of sound in air = = Mach (number) = The speed of sound in water = The speed of sound in steel rod = 1.61 km/hr 1.47 ft/sec 0.87 knots 6080.27 ft/hr (1 nautical mile/hr) about 186,000 mi./sec. 299,790 km/sec. 299,792.8 km/sec. 1087 ft./sec. at 32° F. (741 mph) 1140 ft./sec. at 80° F. (777 mph) speed / speed of sound 4794 ft./sec. at 66° F. 16,410 ft./sec. The speed of sound in air increases with temperature, about 1.1 ft./sec./F. So, at lower altitudes, it is more difficult to 'break the sound barrier'. The speed of sound in liquids and solids is not appreciably changed with temperature. Also see Temperature Drop w/ Altitude Increase

 BMI - Body Mass Index: Body Mass Index is a method of appoximating how overweight or underweight a person is. The rather simplistic approach is subject to errors, yet provides a method the average person can use, requiring no equipment beyond a ruler and bathscale. First, determine your height, in inches, then your weight, in pounds. Now multiply your height times itself (NOT times 2). So 5' 7" is 67 X 67 = 4489. Remember that figure. Now take your weight and divide it by that previous figure. Finally multiply by 703. The result is your BMI. An example - a person weighing 150 lbs., standing 5' 7" tall: 5' 7" is 67", and 67 X 67 = 4489. 150, divide by 4489 = 0.033415 X 703 = 23.49 BMI. The BMI Scale - Less than 18 = 18-25 = 25-29 = 30-40 = Greater than 40 = (What those numbers mean) Underweight Healthy Overweight Obese Morbidly Obese There is a lot of controversy about the accuracy of the scale. Some think it should be adjusted upwards, others think it should be even more draconian. The original formula, using metric measurements: BMI = (weight in kilograms (kg.) / (height in meters) ^ 2) Revised for English: BMI = (weight in lbs. / (height in inches) ^ 2) X 703 Example: 5' 2" and 150 lbs. person Height in inches = 62, 62 squared = (62 X 62 =) 3844 150 lbs / 3844 = 0.0390218 Multiply by 703 = 27.43 BMI. Note - The formula to determine the weight for a given BMI is: Weight = (BMI / 703) X (height in inches) ^ 2 A 5' 7" person is classed as healthy until they reach what weight? 'Healthy' BMI is up to 25. So 25 / 703 X 4489 = 160 lbs.

 Bed and Mattress Measurements: US Standard Mattress Sizes - Crib = Twin = Twin XL = 3/4 = Full = Full XL = Queen = King = CA / Western King = Width X Length (in Inches) 28" X 52" 39" X 75"   (20" X 26" pillow) 39" X 80"   (20" X 26" pillow) 48" X 75"   (20" X 26" pillow) 54" X 75"   (20" X 26" pillow) 54" X 80"   (20" X 26" pillow) 60" X 80"   (20" X 30" pillow) 78" X 80"   (20" X 36-40" pillow) 72" X 84"   (20" X 36-40" pillow) E-King is the standard King or Eastern King (may be only 76" wide) C-King is the California / Western King Super Single is the 3/4 size Twin XL is 1/2 King size Some manufacturers are adding or subtracting inches from these standard sizes, BE SURE to choose a mattress made by a company that can at least use a ruler!! - Else your sheets won't fit correctly! Air Beds (inflatable) are very seldom these exact sizes and vary widely. Mattress thicknesses are about 7" (old) to 10" (new) to 16+" (pillowtop). Box spring thicknesses are typically 5.5" (old) and 7.5" (new). Measure the length of your legs to see if you'll need a step to get in bed. For safety and convenience, one's mattress should not be higher than one's crotch. A typical California King WaterBed holds about 270 Gallons of water, and weighs about 2300 lbs (a little more than a ton).

 Paper Measurements: 1 quire = 1 ream (480 sheets) = 1 ream (commercial) = 1 bundle = 1 bale = 24 sheets 20 quires 500 sheets 2 reams 5 bundles

 Circular Measurements: 1 minute = 1 degree = 1 degree = 1 sextant = 1 quadrant = 1 circumference = 6000 (Soviet) mils = 6400 (U.S.) mils = 4000 (French) decigrades = 60 seconds 60 minutes 17.777   U.S. 'angular' mils * 60 degrees 90 degrees 360 degrees 360 degrees 360 degrees 360 degrees In ancient astronomy, 1 sign = 30 degrees, 12 signs in a circle. What's your sign? * mils -- short for milli-radian or 1/1000th a radian. A circle has 2 pi radians, about 6.238 radians or 6238 milli-radians, which was made simpler by rounding to 6400 (U.S.), or to 6000 (Soviet), or to 6300 (Swedish). NATO forces use ONLY 6400... Errors making optical distance measurements are greater than these round-off errors. See Circular mils in Wire sizes.

 Pressure Measurements: 1 atmosphere = = = = = = 1 torr = 1 pascal (Pa.) = 1 psi. = 1 psi. = 7.03 kg./sq. cm. = 1 kg./sq. cm. = 14.696 pounds/square inch (psi.) 29.92 in. of mercury (Hg.) 760 mm. of mercury (Hg.) 33.94 ft. of water (H2O) 2116.35 pounds/square foot (psf.) 1.01327 bar or 1013.27 millibars (mb.) 1 / 760th atmosphere (1 mm. Hg.)     (Almost a perfect vacuum) 1 Newton/sq. meter 6894.8 pascals 0.07 kg./sq. cm. (Used with Gauges) 100 psi. 14.22 psi.

 Roman Numerals: Decimal     1 = 2 = 3 = 4 = 5 = 6 = 7 = 8 = 9 = 10 = 50 = 100 = 1000 = Roman I II III IV V VI VII VIII IX X L C M The general rules for Roman numerals are: When a symbol precedes one having a greater value, it subtracts from the first, as: IV=4 When a symbol follows one of equal or greater value, it adds to the value of the first, as: II=2 and VI=6 When a symbol is between two of higher value, it subtracts from the third, as: CIX = 109 When a symbol is repeated, its value is also repeated, as: XX=20, CC=200, CCC=300, LXXX or XXC=80 When a symbol has a horizontal line above it, its value is multiplied by itself or squared. MCMXLIV = 1944, MCMLXXXII = 1982, MXMII = 1992 or MCMLXLII = 1992 or MCMLXXXXII = 1992, and MMIII = 2003 (Notice the first form of 1992 is correct, yet the second is used most often and sometimes the third.) Why do many clocks and watches use 'IIII' instead of 'IV'? I dunno. It may be for symetrical balance or because some Romans used 'IIII' before their kids starting using 'IV'. Big Ben in England uses 'IV'. Did you see any '0' (zeros) in those Roman Numerals?

 Sound - Decibel Loudness: Decibels (dB) 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 Power Ratio 1,000,000 100,000 10,000 1,000 100 10 1 0.1 0.01 0.001 0.0001 0.00001 0.000001 Voltage Ratio 1000 316 100 31.6 10 3.16 1 0.316 0.1 0.0316 0.01 0.00316 0.001 In the strictest sense, decibels are only a ratio of two values. If a unit puts out 100 watts and another unit puts out 10,000 watts, then the ratio is 10000 / 100 or 100. On the Power ratio scale, a 100X difference = 20 dB, where the dB value is the 'log base 10 of the ratio'. For a voltage ratio, where it is 'log base 20 of the ratio', a 100X difference = 40 dB. If you have 200 watts/100 watts = 2 X, or 3 dB, that is, a doubling of the power increases 3 dB. For each 10X increase in power, dB increases +10. You may remember hearing of a decibel rating, or loudness, of jet engines. That may seem to be an absolute value, but is still just a ratio to a fixed reference. For sounds, a '120 dB jet engine' refers to ratio of the loudness of the engine to a reference of 10 ^ -16   watts / cm sq., the faintest sound an average person can hear - or 1/1000000000000000th watt per sq. cm. Electronically, a loudness level of 30 dB is really 30 dBm, or 30 dB above a '1 milliwatt across 600 ohms' reference.
 Sounds     Threshold of Hearing = Whisper = Quiet Office = Automobile = Conversation = Heavy Street Traffic = Elevated Trains, Riveters = Loud Thunder = Threshold of Pain = Decibel Levels 0 dB. 10-20 dB. 20-40 dB. 40-50 dB. 60 dB. 70-80 dB. 90-100 dB. 110 dB. 120 dB. 120 dB is a more convenient value to use than saying '1,000,000,000,000 times louder than the softest sound you can hear'. Don't you agree?

 Calendar Dates: (US) New Year's Day = MLK Birthday = Valentine's Day = President's Day ** = St. Patrick's Day = Easter = Mother's Day = Memorial Day = Father's Day = Fourth of July = Labor Day = Columbus Day = Halloween = Veteran's Day = Thanksgiving = Christmas = January 1st * Third Monday in January * February 14th Third Monday in February * March 17th Always changes each year, see below Second Sunday in May Last Monday in May * Third Sunday in June July 4th * First Monday in September * Second Monday in October * October 31st November 11th * Last Thursday in November * December 25th * * Federal Holiday ** Also known as Washington's Birthday Daylight Savings Date Changes Starting in 2007: Daylight Savings begins on the second Sunday in March at 2:00AM.         Set clocks ahead one hour. (SPRING forward) Daylight Savings ends on the first Sunday in November at 2:00AM.         Set clocks back one hour. (FALL back) (Prior to 2007, the change was on the first Sunday in April and last in October, which was 4 weeks less of Daylight Savings than now.) Other Date Trivia How is the date for Easter determined? It changes from year to year. As decreed by the first Council of Nicea in A.D. 325, Easter is observed on the Sunday after the first full moon, on or after the vernal equinox, a range of 35 days. It cannot be before March 22 or after April 25. What is the Julian Date? Used by astronomers, it arbitrarily sets Jan 1, 4713 B.C. as the 0 reference. So Mar 16, 1997 is 2440523.5 Julian. The Julian day starts at noon, we start at midnight, hence the 0.5 on the end. There was no year '0000'. The year 1 A.D. immediately followed the year 1 B.C. What is the Julian Day? The sequentially number day of the year, starting with 1 for Jan 1st, and ending with 365 or 366. Some calendars show both the Julian Day and the inverse - the number of days until the END of the year. Used for calculating the 'days between dates'. When was the current Gregorian Calendar started? It was the day after Thursday Oct 4, 1582, which happened to become Friday Oct 15, 1582! The 10 day 'adjustment' was necessary to get back in step with the sun - landlords loved it, renters hated that change, creating a 21 day month for October, 1582! BUT that was only for Catholic countries following Pope Gregory XIII. England didn't change until Sept 2, 1752 and jumped to Sept 14, 1752. By then the error had increased to 11 days!! Leap Years occur every 4 years (in years evenly divisible by 4), where one extra day is added to February, making it 29 days long. Exactly every 100 years (in years evenly divisible by 100), it should be a Leap Year, but they SKIP the extra day in those years. EXCEPT every 400 years (like 2000), where they ADD the SKIPPED Leap Year day back -- as they did in our year 2000.

 Times: Sun position = Sun position (corrected) = Universal Time (UT0) = (UT1 and UT2) = UT1 = Apparent motion of distant star = Atomic Time (AT) = Coordinated Universal Time (UTC) = Apparent solar time Mean solar time Mean solar time at the Greenwich Meridian     (Greenwich Mean Time or GMT     also known as Zulu Time or Z) (corrected) more accurate versions of UT0 Navigator's time scale Sidereal time Derived from frequency of cesium atoms Weighted average of various Atomic Times,     (GMT for the average person) Passing Time The Atomic Clock allows the measurement of time and frequency to an accuracy much greater than any other physical quantity. Note: GMT starts at noon while UTC starts at midnight. By international agreement, UTC is kept within 0.7 seconds of UT1, by adding and subtracting 'leap seconds' from time to time. The abbreviation of 'Coordinated Universal Time' is indeed, UTC. All GMT and UTC derived times are in the 24HR format, 00:00 to 23:59. The terms 'AM' and 'PM' are abbreviations for Ante-Meridian, meaning 'before the sun reaches the meridian or directly overhead', and Post-Meridian, 'after the sun reaches the meridian'. In 1928, Greenwich Mean Time (GMT) was changed to Universal Time. Before 1956, a second was defined as 1/86,400 of the mean solar day. Then from 1956 to 1967, it was the ephemeris second, defined as 1 / 31556925.9747 of the tropical year at 00h 00m 00s 31 December 1899. Currently the second is defined as 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. TIME REVERSAL INVARIANCE is a type of reversibility that states if time could run backwards, where reversing time corresponds to reversing velocities, and collisions of idealized billiard balls would retrace their paths.

 Military Time Zones: Zulu Time (same as UT) is used by the military and civilian aviation. The term Zulu is phonetic for Z, and Z represents the time zone at the Royal Greenwich Observatory located in Greenwich, England and is also known as Greenwich Mean Time or GMT. Other time zones also have letter designations, from A-Z. Listed below are the phonetic pronunciations for those letters: Zulu in Greenwich, England Zulu Eastward Alpha Bravo Charlie Delta Echo Foxtrot Golf Hotel India     (Japan) Kilo Lima Mike     (Int. Date Line) Zulu Westward November Oscar Papa Quebec Romeo     (Eastern Time Zone) Sierra       (Central) Tango       (Mountain) Uniform     (Pacific) Victor       (Alaskan) Whiskey   (Hawaiian) X-Ray Yankee     (Int. Date Line) The letter designations actually circumvent the globe. All letters are used except "J". Do your math. There are 24 hours in a day, 24 time zones around the globe and 26 letters - 1 = 25. Why do we need 25 letters to name 24 zones? First, Zulu is the zone centered on the Prime Meridian, 0° longitude, Greenwich, England. Each time zone is 15° (360° / 24 hours = 15°). So the Zulu time zone extends 7.5° of longitude east and west from the Prime Meridian. The center of the next time zone east of Zulu is 15°E longitude and is designated A or 'Alpha'. There are 12 time zones going east from Zulu - Alpha to Mike, covering Europe, Russia, China, and the Pacific Basin to the International Date Line. Going WEST from Zulu in England, begins with November, and on to Romeo (for the Eastern time zone in the U.S.), to Uniform (Pacific time), and ends with Yankee at the International Date Line, which is -12 hours from Zulu. Here we have the descrepancy, Zulu is a time zone, and +12 zones eastward brings us to Mike which covers the International Date Line. But going west from Zulu, we ALSO have -12 zones bringing us to Yankee which covers the International Date Line. That totals 12 zones one direction, 12 the other, and with one to start = 25 zones, and we know we only have room for 24! Would it be correct to say, that the one zone over the International Date Line is really divided into halves? Perhaps Mike and Yankee are only half-sized zones? The real answer is: in the single zone named both Mike and Yankee, it is always the exact same time (12 hours offset from Zulu), but it is never the same date!   Each side of the International Date Line is a different day, and the designation of Mike or Yankee for that same time zone indicates which is the correct date, within that zone. And what ever happened to J, the time zone Juliet? That designation is reserved for the local time zone of the observer. If the correct time for the Pacific Time Zone (Uniform) is 9:00 AM, and you are there, then Juliet time, for YOU, is 0900.

 Latitude and Longitude (and GPS): Latitude lines are East and West around the Earth and NEVER meet, therefore they stay the same distance apart as you travel towards each pole -- approximately 69.11 miles for each degree. (68.707 at the equator and 69.407 at the poles). Longitude lines are North and South and MEET at the poles, therefore they are separated the furtherest at the equator and intersect at the poles -- approximately 69.11 miles apart at the equator and only 1.2 miles apart at 89° North. (At 90° North (North Pole) they are separated by 0 miles.) When the Latitude is in the Northern Hemisphere, it's a positive value, and a negative value for the Southern Hemisphere. The Longitude is positive traveling East of England (Greenwich Prime Meridian). Traveling West to the U.S. becomes a negative number. Do I need to say the Latitude and Longitude lines are invisible? I DO need to mention these figures are based on a circular Earth. Most of us know it's not flat anymore, but it's not really round, and it's not elliptical either. It's a biaxial-ellipsoid. And it's not smooth, there are valleys and mountains. None of those are accounted for in these calculations. Hint: most smart phones, tablets, and GPS units ALSO don't calculate elevation correctly and certainly not accurately. OK, if I'm in Atlanta, near the 34th degree of Latitude, how far apart are the Longitude lines around here? You'll need a scientific calculator, either hand-held, app-held, or website, with a Cosine function. And WATCH, we're going to do some astrophysical calculations!!! Enter your Latitude, in this case "34", press the Cosine key/button/icon, and you'll see "0.829...". Press the multiply key/button/icon, and enter "69.11" and you'll see "57.294..." You're done. Longitude lines crossing 34° Latitude are 57.294 miles apart. And, Latitude lines are 69.11 miles apart. How does this relate to GPS values? Most GPS devices can display your position in at least two formats: Decimal Degrees (34.03917° - usually with 5-6 digits after the decimal) or Deg / Min / Sec (34° 02' 21") When these numbers change by one digit, HOW FAR would that be on the Earth? If you move North or South (Latitude change), each degree is 69.11 miles. So 69.11 miles multiplied by 5280 feet = 364900.8 feet. If the Latitude changes from "34.03917" to "34.03918", that was a .00001 change or 1/100,000. Simply take the 364900.8 feet between Latitude lines and divide by 100,000 = 3.64. That's 3.64 feet for every digit change. If the decimal degrees had 6 digits, then you'd divide by 1,000,000 and arrive at 0.364 feet or 4.368 inches... For Deg/Min/Sec values, there are 60 minutes in a degree and 60 seconds in a minute, or 3600 seconds in a degree. We know 364900.8 feet per Latitude degree, so divide it now by 3600 = 101.36. That's 101.36 feet for each digit change in seconds. So, the Decimal Degree format is more accurate? Yes and No -- Yes, it COULD be, NO it's NOT necessarily. Consumer GPS units are designed for 3 meter accuracy or better, which is almost 10 feet. Some MAY be more accurate. It depends on how many satellites it can lock onto, the signal levels, and the instrument. Consumer GPS units aren't very repeatable. That is, take a reading HERE, walk over THERE, then come back HERE, and the reading probably won't be the same. The least digit in the Decimal format is 3.6 feet but the GPS resolution is 3 meters, nearly 3 times that. The Deg / Min / Sec format can display about a 100 foot change, which is 10 times more coarse than the 3 meter GPS accuracy, so that figure will change less.

 Practical Measurement Trivia : Diameter of circle = multiply the circumference by 0.31831 Circumference of a circle = multiply the diameter by 3.1416 Area of a circle = multiply the square of the diameter by .7854 Surface of a ball = multiply the square of the diameter by 3.1416 Cubic volume in a ball = multiply the diameter by 0.8862 Doubling the diameter of a pipe quadruples its capacity. Water pressure (lb/sq in.) = multiply height of column (ft.) by 0.434 pi = 3.1416 OR "Divide 113 INTO 355" (113355, get it?) (355/113 = 3.1415929...) which IS close to pi, for 6 decimal places. OR go here for pi to 1 MILLION decimal places. "Sir, I send a rhyme excelling In sacred truth and rigid spelling Numerical sprites elucidate For me the lexicon's dull weight" Encoded in this poetry: the transcendental number pi to 20 places. Just count the number of letters in each word: three, one, four, one, five, nine ... Did you know?   111,111,111  X  111,111,111  = 12345678987654321

 Impractical Measurement Trivia: Ratio of an igloo's circumference         to its diameter = Jack-o-lantern's circumference,         divided by its diameter = 2.4 statute miles of intravenous         surgical tubing at         Yale University Hospital = Time between slipping on a peel         and smacking the pavement = Time it takes to sail 220 yards         at 1 nautical mile per hour = Midget fortune-teller, escaped from prison = Weight an evangelist carries with God = Shortest distance between two jokes = Australian Local Area Network = 2000 pounds of Chinese soup = 2 erections on the same day = 16.5 feet in the Twilight Zone = 1000 milliliters of wet socks = 1 millionth of a mouthwash = No purchase of either item = Two wrongs by the sister = Going back four seconds = 1 kilogram of falling figs = 453.6 graham crackers = The trendiest story told = Half of a large intestine = Basic unit of laryngitis = Catalog listing 2 items = Catalog listing 1 item = 1 million microphones = 1 duplicate mustard = 2000 mockingbirds = 1 millionth of a fish = 1 distant message = 1 million bicycles = 1,000,000 aches = 1 grandmother = 2 Italian bowls = 2 meters long = 2 monograms = 1 trillion pins = 365.25 days = 100 rations = 10 rations = 1 popcorn = 2 doctors = 8 nickels = 52 cards = Morning = Eternity = Infantry = 1 uncle = Baud = Baud Rate = 100 Senators = Eskimo pi Pumpkin pi 1 IV League 1 Bananosecond Knot-furlong 1 small medium at large 1 billigram Straight line LAN down under Won ton 1 direction 1 Rod Serling 1 literhosen 1 microscope 1 binary 1 parasynthesis 1 hungry clock 1 fig-newton 1 pound cake 1 Inversion 1 semicolon 1 hoarsepower 1 dialogue 1 monologue 1 megaphone 1 Dijon-vu 2 kilomockingbirds 1 microfiche 1 telegram 2 megacycles 1 megahurtz 1 monogram 1 parabola 1 diameter 1 diagram 1 terrapin 1 unicycle 1 C-ration 1 decoration 1 father of a unicorn 1 paradox 2 paradigms 1 decacards Dawn of a new error 4 blondes at a 4-way stop 1 sapling 1 monocle Woman on the street How much she charges Not 1 decision