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Approximate Conversions from U.S. Customary Measures to Metric

The numerical value of the units in the When You Know column are multiplied by the approximate unit conversion factor found in the Multiply By column to obtain a numerical value for the units listed in the To Find Column. For example:

When You Know Multiply By To Find
20 yd 0.91 approximately 18.2 m


Symbol When You Know Multiply By To Find Symbol
in inch 2.54 centimeter cm
ft foot 30.48 centimeter cm
yd yard 0.91 meter m
mi mile 1.61 kilometer km


Symbol When You Know Multiply By To Find Symbol
in² square inch 6.45 square centimeter cm²
ft² square foot 0.09 square meter
yd² square yard 0.84 square meter
mi² square mile 2.59 square kilometer km²
  acre 0.41 hectare ha

Mass (weight)

Symbol When You Know Multiply By To Find Symbol
oz ounce 28.35 gram g
lb pound 0.45 kilogram kg
  short ton
(2000 lb)
0.91 metric ton t


Symbol When You Know Multiply By To Find Symbol
tsp teaspoon 4.93 milliliter mL
Tbsp tablespoon 14.79 milliliter mL
in³ cubic inch 16.39 milliliter mL
fl oz fluid ounce 29.57 milliliter mL
c cup 0.24 liter L
pt pint, liquid 0.47 liter L
qt quart, liquid 0.95 liter L
gal gallon 3.79 liter L
ft³ cubic foot 0.03 cubic meter
yd³ cubic yard 0.76 cubic meter

Temperature (exact)

Symbol When You Know Calculation To Find Symbol
°F degree Fahrenheit subtract 32, then 
divide by 1.8
degree Celsius °C
°F  degree Fahrenheit subtract 32, divide by 1.8, add 273.15 Kelvin K


Metric to U.S. Customary Conversions

Image of NIST SP 365-ConversionCard-A-2019-02
Credit: NIST

Unit conversion is a multi-step process that involves multiplication or division by a numerical factor; selection of the correct number of significant digits; and rounding. Accurate unit conversions are obtained by selecting an appropriate conversion factor (a ratio which converts one unit of measure into another without changing the quantity). 

Note: These approximate approximate conversion factors are published as NIST SP 365, which is a laminated metric conversion card. Copies of this publication can be requested by contacting theSI [at] (theSI[at]nist[dot]gov)



Created January 13, 2010, Updated September 15, 2023