Don's Home Reference Weights & Measure Conversion factors and equivalents Contact 
See also Measurement in tech for definitions.
Common Conversions: Most of the world has converted to the metric system of measurement [milimeter, meter, kilometer, liter, gram, kilogram ...], but the U.S. is the only significant holdout. It and a few of it's Caribbean neighbors are still on the English Customary Weights and Measures [inch, foot, yard, mile, gallon, pound, ...]. Size/distance measure in this system is refered to as standard, Inch or SAE (Society of Automotive Engineers)  
Distance: inch = 2.5400 cm [1 cm = 0.39370 in] mil = 1/1,000 (.001) in mil = 25.4 micrometer/micron (µm) 1 yd = .91440 meter (m) [1 m = 1.093 613 yd] mile = 1.609 344 km = 5,280 ft See size for millimeter (mm), micrometer/micron (µm), etc. chain (Gunter, surveyor's, UK) = 66 ft (18th century US land records) chain (Ramsden, engineer, US) = 100 ft chain = 100 links AU (Astronomical Unit) = 92.96 M mi LY lightyear = 9.46x10^{12} See Also Bolt Size Speed: 1 MPH = 1.467 ft/s 1 MPH = 1.609 km/hr = 0.447 m/s 1 km/h = 0.2778 m/s 1 knot = 1.151 MPH Volume: liter = 1/1,000 m^{3} = 61.0 in^{3} = 0.2642 gal gallon (US) = 3.785 liter gallon = 231 in^{3} = 128 oz Imperialgallon (galUK) = 1.201 gallon (US) liquidquart (qt)= 0.946 liter quartdry (qtdry)= 1.101 liter oz = 29.57 cm^{3} 4 quart / gallon 2 pints / quart 2 cups / pint 16 oz / pint 8 oz / cup 1 1/2 oz / jigger 2 tablespoon (tbsp) / oz 3 teaspoon (tsp) / tbsp barrel (petroleum, US) = 42 gallons (beer, US) = 31 gallons peck = 8 quartsdry bushel = 4 pecks = 35.239 L Imperial bushel = 36.368 L Area: 1 acre = 43,560 sq ft 1 sq mi = 640 acres 1 sq km = 247.1 acre 1 hectare = 2.471 acre See bar measurements in drinks Flow: 1 gpm = 0.134 ft^{3}/min (cu. ft/min.) 
Weight and Mass: 1 pound (lb) = .4536 kg [1 kg=2.205 lbs] 1 short ton = 2,000 lbs (actually 2000.00000014 lbs.) 1 long ton = 2,240 lbs 1 metric ton = 1,000 kg = 2,205 lbs 1 gallon of water = 8.337 lbs Force: 1 newton (N) = 0.2248 poundforce 1 kilonewton (kN) = 224.8 lb Energy  Work: 1 joule = 1 Newton meter (Nm)= 0.7376 ft lb 1 foot pound = 1.356 joule 1 calorie (kcal*) [I.T.] = 4.187 joule 1 calorie (kcal) [I.T.] = 0.003 968 Btu 1 Btu = 252.0 calorie [I.T.] Power: 1 horsepower = 1,980,000 foot poundforce/hour 1 watt = 860 calories/hour Pressure: 1 lb/in^{2} (PSI) = 6.89 kilopascal (kPa) 1 PSI = 2.31 feet head of water 1 PSI = 2.04 in mercury (inHg) 1 N/mm^{2} = 145.03 PSI 1 Barr = 15 PSI 1 Atmosphere = 2,116 lb/ft^{2} = 14.70 lb/in^{2} 1 in mercury = 70.7 lb/ft^{2} = 0.491 lb/in^{2} 1 lb/ft^{2} = 4.882 kg/mSUP>2 Angular: 1 degree (°) = π/180 (.01745) radians 1 radian = 57.30° degrees 1 minute (') = 1/60 degree 1 sec (") = 1/60 minute 1 mil=angle whose tangent is 1/1000=.0573° (i.e. 1 mil at 1 km is 1 m) 1 point = 11.25° [ 8 points = 90°] Temperature: Fahrenheight (F) = 1.8*C + 32 (1.8 = 9/5) Celcius (C) = (F32) / 1.8 Kelvin (K) = C + 273
Illuminance: (degree to which something is illuminated) 1 Footcandle = 1 Lumen (lm)/sq ft 1 Lumen/sq ft = 10.76 LUX (lx) (lumens/sq m)Radiance/Luminous Intensity: (energy at light source) 1 candlepower (CANDELA) (cd) = 12.57 lumens (lm) Surface area of a sphere with radius of 1 ft. is 12.57 sq. ft. 1 watt = 683 lumens (@ 555nm [green]) See Light Brightness Note: Candlepower has been incorrectly used by flashlight manufactures to exaggerate their power.  
* kcal  kilocalorie = Amount of heat
requird to raise one kilogram of water
by one degree Celsius. The small calorie (gram calorie) is 1/1000 kcal. Sometimes Calorie (capital C) is used to distinguish kcal from calorie. When used in the context of food energy the term Calorie generally refers to the kilogram calorie.
Reference Standard: In 1960, scientists defined the meter in terms of the wavelength of a specific orange light emitted by krypton atoms. In 1983, they redefined the speed of light to be exactly 299,792,458 meters per second, so a meter is now just the distance that light travels in a vacuum in 1/299,792,458th of a second. A platinumiridium cylinder about the size of a plum LOCKED in a vault in Paris was established as the official definition of the kilogram, in 1889.
In 2005 Scientists at the National Institute of Standards and Technology in Gaithersburg, Md., announced significant progress toward supplanting this cylinder.
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