necro-uom-icon

units-of-measure for smarties

Unit Converter

=

Major Systems

sorted by relevance according to a nonentity

International System of Units

I'll call it the metric system, it is abbreviated as SI (from the French Systeme International d'Unites). If we had to pick a single system, this would be our best bet. What it lacks in whimsy, it makes up for in coherence.

English Units of Measurement

England's measurement system, abandonware since 1826, but the mother system of Imperial and USCS

Imperial

the post-1824 measures used in the British Empire and countries in the British sphere of influence

United States Customary System

freedom units, I'll call them USCS.

Gripes on the major systems and software menus - A lot of software in the world with a single UOM option will only let you pick between Metric or Imperial. Maybe this is suitable if you are living in a confused time in England, where diferent systems are used in different situations. This is admittedly fine for a couple of cases (mph vs. kph, Celsius vs. Fahrenheit) but it is un-American for you (iPhone®) to make me pick British units for my weather. Luckily Apple® now lets you pick between Metric, UK, and US units (on my phone at least). Imperial units are different than freedom units. Most notably, the Imperial volumes are about 20% more voluminous than the USCS versions (and they don't use cups, they use gills which are 1/4 of an Imperial pint, not to be confused with the USCS gill, which is 4 fluid ounces).

Other Systems

You won't find these in the iPhone® menu, but they are still pretty cool

cgs

centimeters, grams, seconds, often used in the medical sciences

mks

meters, kilograms, seconds, basically engineering units of the metric system

fps

foot, pound, second, used in the U.S., Liberia, and Myanmar

English Engineering Units

USCS, but with extra steps. lbm or slugs for mass, lbf for force

Farming Units

Bushels, pecks, bales, dry pints, acres, hectares

Nautical Units

Nautical mile (exactly 1852 meters), knots (1 nautical mile per hour), fathom (depth, exactly 6 feet)

Electrical Engineering

Computer Memory

Most notably, metric prefixes can be used, but we also like to use powers of 1024 instead of 1000, and we incorrectly call things 1 KB instead of KiB all the time. Usually powers of 1000 are used for storage and powers of 1024 are used for memory.

Anthropometric Units

Hands, feet, cubits, pace, span, inch, fathom (a person's wingspan)

Conversions

USCS and Imperial lengths are identical. Volume is where they diverge.

Length

UnitMetersNotes
Planck length (lP)1.616 x 10^-35 msmallest meaningful length in physics
Fermi (fm)1 x 10^-15 mfemtometer, scale of atomic nuclei
Angstrom (A)1 x 10^-10 mscale of atoms and chemical bonds
Micron (um)1 x 10^-6 mmicrometer, scale of cells and bacteria
Thou (th)2.54 x 10^-5 m1/1000 inch, used in manufacturing
Mil (mil)2.54 x 10^-5 msame as thou, different name
Pixel (px)2.6458 x 10^-4 mCSS reference pixel at 96 DPI; 1px = 1/96 in
Millimeter (mm)0.001 mSI
Centimeter (cm)0.01 mSI
Inch (in)0.0254 m (exact)1/12 foot, USCS/Imperial
Foot (ft)0.3048 m (exact)12 inches, USCS/Imperial
Rod (rd)5.0292 m16.5 feet, also called pole or perch
Yard (yd)0.9144 m (exact)3 feet, USCS/Imperial
Fathom (ftm)1.8288 m6 feet, nautical depth
Chain (ch)20.1168 m66 feet, 4 rods, surveying unit
Meter (m)1 mSI base unit
American football field91.44 m100 yards, end zones not included
FIFA pitch length105 mstandard international match length
Kilometer (km)1,000 mSI
Mile (mi)1,609.344 m5,280 feet, USCS/Imperial
League, English4,828.032 m3 miles
Nautical mile (nmi)1,852 m (exact)1 arcminute of latitude
Earth radius (R)6,371,000 mmean radius
Lunar distance (LD)384,400,000 mmean Earth-Moon distance
Astronomical unit (AU)1.496 x 10^11 mmean Earth-Sun distance, exact by IAU definition
Light year (ly)9.461 x 10^15 mdistance light travels in one year
Parsec (pc)3.086 x 10^16 m3.26 light years, 648,000/pi AU

Volume - USCS

UnitLitersNotes
Drop0.05 mL~0.05 mL, varies by dropper
Teaspoon (tsp)4.929 mL1/6 fl oz
Tablespoon (tbsp)14.787 mL3 tsp, 1/2 fl oz
Fluid ounce (fl oz)29.574 mL1/128 gallon
Shot (jigger)44.360 mL1.5 fl oz
Cup236.6 mL8 fl oz
Pint (pt)473.2 mL16 fl oz
Quart (qt)946.4 mL2 pints
Gallon (gal)3.785 L128 fl oz, 4 quarts
Cubic inch (in3)16.387 mLused in engine displacement
Cubic foot (ft3)28.317 L1,728 in3
Cubic yard (yd3)764.6 L27 ft3; concrete and mulch
Peck US (pk)8.810 L1/4 bushel; dry goods
Bushel US (bu)35.239 L4 pecks; grain, produce
Barrel, petroleum (bbl)158.987 L42 US gallons; crude oil standard
Hogshead (US)238.481 L63 US gallons; wine and tobacco
Acre-foot1,233,480 Lwater rights and reservoir capacity

Volume - Imperial

Imperial volumes are about 20% larger than USCS. No cups - they use gills (1/4 Imperial pint). The USCS gill (4 fl oz) is also different.
UnitLitersvs. USCS
Fluid ounce28.413 mL4% smaller than USCS fl oz
Gill142.1 mL5 Imperial fl oz; no USCS cup equivalent
Pint568.3 mL20 fl oz; 20% bigger than US pint
Quart1136.5 mL20% bigger than US quart
Gallon4.546 L20% bigger than US gallon

Volume - Reference

ThingVolumeNotes
Wine bottle (standard)750 mL25.4 fl oz US
Human blood volume5 Ladult average
Average human body70 Lvaries; mostly water
Bathtub (avg)300 L~80 US gallons
Olympic swimming pool2,500,000 L50 m x 25 m x 2 m
Lake Superior1.21 x 10^16 L12,100 km3; largest Great Lake by surface area
Pacific Ocean7.1 x 10^20 L710,000,000 km3; largest ocean
Earth (volume)1.08 x 10^24 L1.08 x 10^12 km3

Mass

USCS and Imperial mass units are the same except for the ton. Avoirdupois is the everyday system (pounds, ounces); troy is used for precious metals.

UnitKilogramsNotes
Electron mass9.109 x 10^-31 kgrest mass of an electron
Atomic mass unit (u, Da)1.661 x 10^-27 kg1/12 mass of carbon-12 atom; also called Dalton
Nanogram (ng)1 x 10^-12 kgSI
Microgram (ug)1 x 10^-9 kgSI; pharmaceutical dosing
Planck mass2.176 x 10^-8 kgnatural unit of mass (~21.76 ug)
Milligram (mg)1 x 10^-6 kgSI; medication dosing
Centigram (cg)1 x 10^-5 kgSI
Grain (gr)6.480 x 10^-5 kg64.799 mg; base of avoirdupois and troy; used in ballistics
Carat, metric (ct)2 x 10^-4 kg200 mg; gemstone weight
Gram (g)0.001 kgSI; 15.432 grains
Dram, avoirdupois (dr)0.001772 kg1/16 oz; used in pharmacy historically
Mole of H20.002016 kg2.016 g; molar mass of diatomic hydrogen (H2)
US Penny0.002500 kg2.5 g; 97.5% zinc, 2.5% copper; 19.05 mm diameter
Hummingbird0.003 kg3 g; typical Ruby-throated hummingbird
Ounce, avoirdupois (oz)0.028350 kg1/16 lb; everyday US/UK weight
Ounce, troy (oz t)0.031103 kg1/12 troy lb; gold, silver, gems
Pound, troy (lb t)0.373242 kg12 troy oz; precious metals
Pound, avoirdupois (lb)0.453592 kg16 oz; everyday US/UK weight
Stone (st)6.350 kg14 lb; body weight in UK/Ireland
Slug14.594 kgFPS unit; mass accelerated at 1 ft/s2 by 1 lbf
Hundredweight, short (US)45.359 kg100 lb
Hundredweight, long (UK)50.802 kg112 lb
Kilogram (kg)1 kgSI base unit
Adult human (avg)70 kg154 lb
Short ton, US907.185 kg2,000 lb
Metric tonne (t)1,000 kg2,204.62 lb
Long ton, Imperial1,016.047 kg2,240 lb
Typical passenger car2,000 kg2 metric tonnes
Average single-family home45,359 kg50 short tons
Blue whale (avg)150,000 kg150 tonnes; largest animal ever
Great Pyramid of Giza6 x 10^9 kg6 million tonnes
Total human biomass6 x 10^11 kg600 million tonnes, all ~8 billion people
Earth mass5.972 x 10^24 kgused in planetary science
Jupiter mass1.898 x 10^27 kgabout 318 Earth masses
Solar mass1.989 x 10^30 kgstandard unit in astronomy; about 1,048 Jupiter masses

Time

UnitSecondsNotes
Planck time5.391 x 10^-44 ssmallest meaningful time interval in physics
Jiffy33.356 pstime for light to travel 1 cm in a vacuum
Nanosecond (ns)1 x 10^-9 slight travels ~30 cm; CPU clock cycle scale
Shake10 nsnuclear physics slang; used in weapons design
Microsecond (us)1 x 10^-6 sSI
Millisecond (ms)0.001 shuman reaction time is ~150-300 ms
Blink of an eye~0.15 s100-400 ms depending on who you ask
Second (s)1 sSI base unit
Microfortnight1.2096 sone millionth of a fortnight; hacker culture unit
Nanocentury3.156 sone billionth of a century; another hacker unit
Minute (min)60 s60 seconds
Moment90 smedieval unit; 1/40 of an hour
Hour (hr)3,600 s60 minutes
Sidereal day86,164 sone full Earth rotation relative to distant stars; ~4 min shorter than a solar day
Day86,400 s24 hours; solar day
Week604,800 s7 days
Megasecond1,000,000 s~11.57 days; SI prefix
Fortnight1,209,600 s2 weeks; common in British English
Month (avg)2,629,746 s365.25/12 days
Dog year4,508,143 s1/7 of a human year
Mercury year7,600,530 s87.97 days
Venus year19,414,166 s224.70 days
Earth year (Julian)31,557,600 s365.25 days
Mars year59,354,534 s686.97 days (~1.88 Earth years)
Olympiad126,230,400 s4 years; interval between Olympic games
Decade315,576,000 s10 years
Jupiter year374,335,690 s4,332.59 days (~11.86 Earth years)
Indiction473,364,000 s15 years; Roman taxation assessment cycle
Score631,152,000 s20 years; "four score and seven years ago"
Saturn year929,596,608 s10,759.22 days (~29.46 Earth years)
Human lifespan (avg)~2.49 x 10^9 s~79 years globally
Uranus year2,651,486,400 s30,688.5 days (~84.01 Earth years)
Century3,155,760,000 s100 years
Neptune year5,199,724,800 s60,182 days (~164.8 Earth years)
Millennium3.156 x 10^10 s1,000 years
Megaannum (Ma)3.156 x 10^13 s1 million years; standard geological unit
Eon3.156 x 10^16 s1 billion years; geological deep time
Age of the Universe4.355 x 10^17 s~13.8 billion years

Temperature

ConversionFormula
F to C(F - 32) x 5/9
C to F(C x 9/5) + 32
C to KC + 273.15
F to K(F - 32) x 5/9 + 273.15
Quick check: 0C = 32F (freezing), 100C = 212F (boiling), 37C = 98.6F (body temp).

Area

Unitm2Notes
square millimeter (mm2)0.000001
square centimeter (cm2)0.0001
square inch (in2)0.00064516
square foot (ft2)0.092903144 in2
square yard (yd2)0.8361279 ft2
square meter (m2)1
acre4,046.8643,560 ft2
hectare (ha)10,0002.471 acres
square kilometer (km2)1,000,000100 ha
square mile (mi2)2,589,988640 acres

Area - Reference

Areakm2Notes
Pool ball surface0.00000000001032.25 in diameter; 4πr2
Washington DC158.1US territory / federal district
Guam544US territory
N. Mariana Islands464US territory
American Samoa199US territory
US Virgin Islands346US territory
Puerto Rico9,104US territory

Area - US States

Statekm2mi2
Rhode Island4,0011,545
Delaware6,4462,489
Connecticut14,3575,543
New Jersey22,5918,722
New Hampshire24,2149,349
Vermont24,9069,616
Massachusetts27,33610,555
Hawaii28,31310,932
Maryland32,13112,407
West Virginia62,75624,230
South Carolina82,93332,020
Maine91,63335,380
Indiana94,32636,420
Kentucky104,65640,408
Tennessee109,15342,144
Virginia110,78742,775
Ohio116,09844,826
Pennsylvania119,28146,055
Mississippi125,43848,432
Alabama135,76752,419
Louisiana135,65952,378
Arkansas137,73253,179
New York141,29754,555
North Carolina139,39153,819
Iowa145,74656,273
Illinois149,99557,914
Georgia153,91059,425
Florida170,31265,758
North Dakota183,10870,698
Oklahoma181,03769,899
Missouri180,54069,707
Wisconsin169,63565,496
Washington184,66171,298
South Dakota199,72977,116
Nebraska200,33077,358
Idaho216,44383,569
Minnesota225,16386,936
Michigan250,48796,714
Oregon254,79998,379
Wyoming253,33597,813
Utah219,88284,897
Colorado269,601104,094
Nevada286,380110,572
New Mexico314,917121,590
Arizona295,234113,990
Montana380,831147,040
California423,967163,696
Texas695,662268,596
Alaska1,723,337665,384

Area - Canada

Province / Territorykm2Notes
Prince Edward Island5,660smallest province
Nova Scotia55,284
New Brunswick72,908
Newfoundland & Labrador405,212
Ontario1,076,395
Quebec1,542,056largest province
Manitoba647,797
Saskatchewan651,036
Alberta661,848
British Columbia944,735
Yukon482,443territory
Northwest Territories1,346,106territory
Nunavut2,093,190largest territory; Canada's newest (1999)
Canada (total)9,984,6702nd largest country in the world

Area - Europe

Countrykm2
Vatican City0.44
Monaco2.02
San Marino61.2
Liechtenstein160
Malta316
Andorra468
Luxembourg2,586
Cyprus9,251
Kosovo10,887
Montenegro13,812
Slovenia20,273
North Macedonia25,713
Albania28,748
Belgium30,528
Italy301,340
Moldova33,846
Denmark43,094
Switzerland41,285
Netherlands41,543
Estonia45,228
Bosnia & Herzegovina51,197
Croatia56,594
Slovakia49,035
Latvia64,589
Lithuania65,300
Ireland70,273
Serbia77,474
Austria83,871
Czech Republic78,866
Hungary93,028
Portugal92,212
Iceland103,000
Bulgaria110,879
Greece131,957
United Kingdom243,610
Romania238,397
Belarus207,600
Poland312,679
Germany357,114
Norway385,207
Finland338,424
Spain505,990
Sweden450,295
Ukraine603,550
Turkey783,562
France551,695

Area - Notable Countries

Countrykm2Notes
Japan377,975
Australia7,692,0246th largest country
China9,596,9603rd largest country
United States9,833,5174th largest country
Canada9,984,6702nd largest country
Russia17,098,242largest country; ~11% of Earth's land
Surface of Earth510,100,000total surface incl. oceans
Surface of the Sun6,083,000,000,000~11,900 x Earth's surface

Plane Angle

UnitRadiansNotes
Second of arc (")4.848e-61/3600 of a degree
Minute of arc (')2.909e-41/60 of a degree
Milliradian (mrad)0.001
Gradian (gon)0.0157081/400 of a full turn; used in surveying
Degree (°)0.0174531/360 of a full turn
Radian (rad)1SI unit; angle subtending arc = radius
Turn / revolution6.283182π rad

Frequency

UnitHzNotes
RPM0.01667cycles per minute
Hertz (Hz)1cycles per second; SI unit
Kilohertz (kHz)1,000AM radio band
Megahertz (MHz)1,000,000FM radio; WiFi 2.4 GHz band
Gigahertz (GHz)1,000,000,000CPU clocks; WiFi 5/6 GHz
Terahertz (THz)1,000,000,000,000between microwave and infrared

Fuel Economy

mpg (US)mpg (Imp)km/LL/100km
1012.04.2523.5
2024.08.5011.8
3036.012.87.84
4048.017.05.88
5060.121.34.70

Note: L/100km is inverse - lower is more efficient. 1 US gallon = 3.785 L; 1 Imperial gallon = 4.546 L.

Digital Storage

UnitBytesNotes
Bit (b)0.125smallest unit
Byte (B)18 bits
Kilobyte (KB)1,000SI; used by storage manufacturers
Kibibyte (KiB)1,024IEC; 2^10; used by OSes
Megabyte (MB)1,000,000SI
Mebibyte (MiB)1,048,576IEC; 2^20
Gigabyte (GB)1,000,000,000SI
Gibibyte (GiB)1,073,741,824IEC; 2^30
Terabyte (TB)1,000,000,000,000SI
Tebibyte (TiB)1,099,511,627,776IEC; 2^40
Petabyte (PB)1,000,000,000,000,000SI
Pebibyte (PiB)1,125,899,906,842,624IEC; 2^50

Data Transfer Rate

UnitBits/secondNotes
Bit/second (bps)1
Byte/second (B/s)8
Kilobit/second (Kbps)1,000older modem speeds
Kilobyte/second (KB/s)8,000
Megabit/second (Mbps)1,000,000home broadband unit
Megabyte/second (MB/s)8,000,000USB 2.0: ~60 MB/s
Gigabit/second (Gbps)1,000,000,000gigabit ethernet; fast fiber
Gigabyte/second (GB/s)8,000,000,000NVMe SSD reads
Terabit/second (Tbps)1,000,000,000,000backbone fiber links