Conversion of units
exactly equal to
approximately equal to
indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369…)
of chiefly historical interest
Conversion of units refers to conversion factors between
different units of measurement for the same quantity.
Rounding of results
The process of making a conversion cannot produce a
more precise result than the original quoted figure. Ap-
propriate rounding of results is normally performed
after conversion. (See significant figures).
Tables of conversion factors
This article gives lists of conversion factors for each of a
number of physical quantities, which are listed in the in-
dex. For each physical quantity, a number of different
units (some only of historical interest) are shown and
expressed in terms of the corresponding SI unit.
Note: see Weight for detail of mass/weight distinction and
In physics, the pound of mass is sometimes written lbm
to distinguish it from the pound-force (lbf). It should not
be read as the mongrel unit "pound metre".
The SI unit for density is:
• kilograms per cubic metre (kg/m3)
Metric units outside the SI
• kilograms per litre (kg/L). Water generally has a
density around 1 kg/L, making this a convenient
• kilograms per cubic decimeter (kg/dm3)
• grams per millilitre (g/mL),
• grams per cubic centimeter (g/cc or g/cm3).
These are numerically equivalent to kg/L (1 kg/L = 1 kg/
dm3 = 1 g/cm3 = 1 g/mL).
In U.S. customary units or Imperial units, the units of
• ounces per cubic inch (oz/cu in)
• pounds per cubic inch (lb/cu in)
• pounds per cubic foot (lb/cu ft)
• pounds per cubic yard (lb/cu yd)
• pounds per gallon (for U.S. or imperial gallons) (lb/
• pounds per U.S. bushel (lb/bu)
• slugs per cubic foot.
Speed or velocity
A velocity consists of a speed combined with a direction;
the speed part of the velocity takes units of speed.