Conversion From U.S. Customary to Metric units

When You Know Multiply By To Find
inches 25.4 millimeters
2.54 centimeters
feet 30.48 centimeters
yards 0.91 meters
miles 1.61 kilometers
teaspoons 4.93 milliliters
tablespoons 14.79 milliliters
fluid ounces 29.57 milliliters
cups 0.24 liters
pints 0.47 liters
quarts 0.95 liters
gallons 3.79 liters
cubic feet 0.028 cubic meters
cubic yards 0.76 cubic meters
ounces 28.35 grams
pounds 0.45 kilograms
short tons (2,000 lbs) 0.91 metric tons
square inches 6.45 square centimeters
square feet 0.09 square meters
square yards 0.84 square meters
square miles 2.60 square kilometers
acres 0.40 hectacres

From Metric to U.S. Customary Units

When You Know Multiply By To Find
millimeters 0.04 inches
centimeters 0.39 inches
meters 3.28 feet
1.09 yards
kilometers 0.62 miles
milliliters 0.20 teaspoons
0.06 tablespoons
0.03 fluid ounces
liters 1.06 quarts
0.26 gallons
4.23 cups
2.12 pints
cubic meters 35.32 cubic feet
1.35 cubic yards
grams 0.035 ounces
kilograms 2.21 pounds
metric ton (1,000 kg) 1.10 short ton
square centimeters 0.16 square inches
square meters 1.20 square yards
square kilometers 0.39 square miles
hectacres 2.47 acres

Temperature Conversion Between Celsius and Fahrenheit

°C = (°F - 32) ÷ 1.8
°F = (°C x 1.8) + 32

Condition Fahrenheit Celsius
Boiling point of water 212° 100°
A very hot day 104° 40°
Normal body temperature 98.6° 37°
A warm day 86° 30°
A mild day 68° 20°
A cool day 50° 10°
Freezing point of water 32° 0°
Lowest temperature Gabriel Fahrenheit could obtain by mixing salt and ice 0° -17.8°

U.S. Customary System: Length

Unit Relation to Other U.S. Customary Units Metric Equivalent
inch 1/12 foot 2.54 centimeters
foot 12 inches or 1/3 yard 0.3048 meter
yard 36 inches or 3 feet 0.9144 meter
rod 16 1/2 feet or 5 1/2 yards 5.0292 meters
furlong 220 yards or 1/8 mile 0.2012 kilometer
mile (statute) 5,280 feet or 1,760 yards 1.6093 kilometers
mile (nautical) 2,025 yards 1.852 kilometers

U.S. Customary System: Volume or Capacity (Liquid Measure)

Unit Relation to Other U.S. Customary Units Metric Equivalent
ounce 1/16 pint 29.574 milliliters
gill 4 ounces 0.1183 liter
pint 16 ounces 0.4732 liter
quart 2 pints or 1/4 gallon 0.9463 liter
gallon 128 ounces or 8 pints 3.7853 liters
barrel
(wine) 31 1/2 gallons 119.24 liters
(beer) 36 gallons 136.27 liters
(oil) 42 gallons 158.98 liters

U.S. Customary System: Volume or Capacity (Dry Measure)

Unit Relation to Other U.S. Customary Units Metric Equivalent
pint 1/2 quart 0.5506 liter
quart 2 pints 1.1012 liters
peck 8 quarts or 1/4 bushel 8.8098 liters
bucket 2 pecks 17.620 liters
bushel 2 buckets or 4 pecks 35.239 liters

U.S. Customary System: Weight

Unit Relation to Other U.S. Customary Units Metric Equivalent
grain 1/7000 pound 64.799 milligrams
dram 1/16 ounce 1.7718 grams
ounce 16 drams 28.350 grams
pound 16 ounces 453.6 grams
ton (short) 2,000 pounds 907.18 kilograms
ton (long) 2,240 pounds 1,016.0 kilograms

U.S. Customary System: Geographic Area

Unit Relation to Other U.S. Customary Units Metric Equivalent
acre 4,840 square yards 4,047 square meters

Cooking Measures

Unit Relation to Other Cooking Measures Conversion to Metric Units
drop 1/76 teaspoon 0.0649 milliliter
teaspoon 76 drops or 1/3 tablespoon 4.9288 milliliters
tablespoon 3 teaspoons 14.786 milliliters
cup 16 tablespoons or 1/2 pint 0.2366 liter
pint 2 cups 0.4732
quart 4 cups or 2 pints 0.9463

British Imperial System: Volume or Capacity (Liquid Measure)

Unit Relation to Other British Imperial Units Conversion to U.S. Customary Units Conversion to Metric Units
pint 1/2 quart 1.201 pints 0.5683 liter
quart 2 pints or 1/4 gallon 1.201 quarts 1.137 liters
gallon 8 pints or 4 quarts 1.201 gallons 4.546 liters

British Imperial System: Volume or Capacity (Dry Measure)

Unit Relation to Other British Imperial Units Conversion to U.S. Customary Units Conversion to Metric Units
peck 1/4 bushel 1.0314 pecks 9.087 liters
bushel 4 pecks 1.0320 bushels 36.369 liters

Apothecary Weights

Unit Relation to Other Apothecary Units Conversion to U.S. Customary Units Conversion to Metric Units
grain 160 dram or 1/5760 pound equal to the U.S. Customary grain 64.799 milligrams
dram 60 grains or 1/8 ounce 2.1943 drams 3.8879 grams
ounce 8 drams 1.0971 ounces 31.1035 grams
pound 12 ounces or 96 drams 0.8232 pound 373.242 grams

Units of the International System

The International System (abbreviated SI, for Systeme International, the French name for the system) was adopted in 1960 by the 11th General Conference on Weights and Measures. An expanded and modified version of the metric system, International System addresses the needs of modern science for additional and more accurate units of measurement. The key features of the International System are decimalization, a system of prefixes, and a standard defined in terms of an invariable physical measure.

Base Units

The International System has base units from which all others in the system are derived. The standards for the base units, except for the kilogram, are defined by unchanging and reproducible physical occurences. For example, the meter is defined as the distance traveled by light in a vacuum in 1/299,792,458 of a second. The standard for the kilogram is a platinum-iridium cylinder kept at the International Bureau of Weights and Standards in Sèvres, France.
Unit Quantity Symbol
meter length m
kilogram mass kg
second time s
ampere electric current A
kelvin temperature K
mole amount of matter mol
candela luminous intensity cd

Supplementary Units

The International System uses two supplementary units that are based on abstract geometrical concepts rather than physical standards.
Unit Quantity Symbol
radian plane angles rad
steradian solid angles sr

Prefixes

A multiple of a unit in the International System is formed by adding a prefix to the name of that unit. The prefixes change the magnitude of the unit by orders of ten from 1024 to 10-24.
Prefix Symbol Multiplying Factor
yotta- Y 1024 = 1,000,000,000,000,000,000,000,000
zetta- Z 1021 = 1,000,000,000,000,000,000,000
exa- E 1018 = 1,000,000,000,000,000,000
peta- P 1015 = 1,000,000,000,000,000
tera- T 1012 = 1,000,000,000,000
giga- G 109 = 1,000,000,000
mega- M 106 = 1,000,000
kilo- K 103 = 1,000
hecto- h 102 = 1000
deca- da 10 = 10
deci- d 10-1 = 0.1
centi- c 10-2 = 0.01
milli- m 10-3 = 0.001
micro- 10-6 = 0.000,001
nano- n 10-9 = 0.000,000,001
pico- p 10-12 = 0.000,000,000,001
femto- f 10-15 = 0.000,000,000,000,001
atto- a 10-18 = 0.000,000,000,000,000,001
zepto- z 10-21 = 0.000,000,000,000,000,000,001
yocto- y 10-24 = 0.000,000,000,000,000,000,000,001

Additional Units

Listed below are a few of the non-SI units that are commonly used with the International System.
Unit Quantity Symbol
angstrom (= 10-10m) length Å
electron-volt (= 0.160 aJ) energy eV
hectare (= 10,000 m2) land area ha
liter (= 1.0dm3) volume or capacity l
standard atmosphere (= 101.3 kPa) pressure atm

Derived Units

Most of the units in the International System are derived units, that is units defined in terms of base units and supplementary units. Derived units can be divided into two groups - those that have a special name and symbol, and those that do not.
Without Names and Symbols
Measure of Derivation
acceleration m/s2
angular acceleration rad/s2
angular velocity rad/s
density kg/m3
electric field strength V/m
luminance cd/m2
magnetic field strength A/m
velocity m/s

With Names and Symbols
Unit Measure of Symbol Derivation
coulomb electric charge C A·s
farad electric capacitance F A·s/V
henry inductance H V·s/A
hertz frequency Hz cycles/s
joule quantity of energy J N·m
lumen flux of light lm cd·sr
lux illumination lx lm/m2
newton force N kg·m/s2
ohm electric resistance V/A
pascal pressure Pa N/m2
tesla magnetic flux density T Wb/m2
volt voltage V W/A
watt power W J/s
weber magnetic flux Wb V·s