Appendix C Units and Conversion Factors

Units of Length

meter (m)	= 39.37 inches (in.) = 1.094 yards (yd)
centimeter (cm)	= 0.01 m (exact, definition)
millimeter (mm)	= 0.001 m (exact, definition)
kilometer (km)	= 1000 m (exact, definition)
angstrom (Å)	= 10^–8 cm (exact, definition) = 10^–10 m (exact, definition)
yard (yd)	= 0.9144 m
inch (in.)	= 2.54 cm (exact, definition)
mile (US)	= 1.60934 km

Table C1

Units of Volume

liter (L)	= 0.001 m³ (exact, definition) = 1000 cm³ (exact, definition) = 1.057 (US) quarts
milliliter (mL)	= 0.001 L (exact, definition) = 1 cm³ (exact, definition)
microliter $(μL)$	= 10^–6 L (exact, definition) = 10^–3 cm³ (exact, definition)
liquid quart (US)	= 32 (US) liquid ounces (exact, definition) = 0.25 (US) gallon (exact, definition) = 0.9463 L
dry quart	= 1.1012 L
cubic foot (US)	= 28.316 L

Table C2

Units of Mass

gram (g)	= 0.001 kg (exact, definition)
milligram (mg)	= 0.001 g (exact, definition)
kilogram (kg)	= 1000 g (exact, definition) = 2.205 lb1 1 Strictly speaking, the ounce and pound are units of weight, W (a force equal to the product of mass and gravitational acceleration, W = mg). The conversion relations in this table are commonly used to equate masses and weight assuming a nominal value for g at the surface of the earth.
ton (metric)	=1000 kg (exact, definition) = 2204.62 lb
ounce (oz)	= 28.35 g
pound (lb)	= 0.4535924 kg
ton (short)	=2000 lb (exact, definition) = 907.185 kg
ton (long)	= 2240 lb (exact, definition) = 1.016 metric ton

Table C3

Units of Energy

4.184 joule (J)	= 1 thermochemical calorie (cal)
1 thermochemical calorie (cal)	= 4.184 $\times$ 10⁷ erg
erg	= 10^–7 J (exact, definition)
electron-volt (eV)	= 1.60218 $\times$ 10⁻¹⁹ J = 23.061 kcal mol⁻¹
liter∙atmosphere	= 24.217 cal = 101.325 J (exact, definition)
nutritional calorie (Cal)	= 1000 cal (exact, definition) = 4184 J
British thermal unit (BTU)	= 1054.804 J2 2 BTU is the amount of energy needed to heat one pound of water by one degree Fahrenheit. Therefore, the exact relationship of BTU to joules and other energy units depends on the temperature at which BTU is measured. 59 °F (15 °C) is the most widely used reference temperature for BTU definition in the United States. At this temperature, the conversion factor is the one provided in this table.

Table C4

Units of Pressure

torr	= 1 mm Hg (exact, definition)
pascal (Pa)	= N m^–2 (exact, definition) = kg m^–1 s^–2 (exact, definition)
atmosphere (atm)	= 760 mm Hg (exact, definition) = 760 torr (exact, definition) = 101,325 N m^–2 (exact, definition) = 101,325 Pa (exact, definition)
bar	= 10⁵ Pa (exact, definition) = 10⁵ kg m^–1 s^–2 (exact, definition)

Table C5