# Appendix C: Units and Conversion Factors

Units of Length
meter (m) =  39.37 inches (in.) angstrom (Å) =  10–8 cm (exact, definition)
meter (m) =  1.094 yards (yd) angstrom (Å) =  10–10 m (exact, definition)
centimeter (cm) =  0.01 m (exact, definition) yard (yd) =  0.9144 m
millimeter (mm) =  0.001 m (exact, definition) inch (in.) =  2.54 cm (exact, definition)
kilometer (km) =  1000 m (exact, definition) mile (US) =  1.60934 km
Units of Volume
liter (L) =  0.001 m3 (exact, definition) liquid quart (US) =  32 (US) liquid ounces (exact, definition)
liter (L) =  1000 cm3 (exact, definition) liquid quart (US) =  0.25 (US) gallon (exact, definition)
liter (L) =  1.057 (US) quarts liquid quart (US) =  0.9463 L
milliliter (mL) =  0.001 L (exact, definition) dry quart =  1.1012 L
milliliter (mL) =  1 cm3 (exact, definition) cubic foot (US) =  28.316 L
microliter (μL) =  10–6 L (exact, definition)
microliter (μL) =  10–3 cm3 (exact, definition)
Units of Mass
gram (g) =  0.001 kg (exact, definition) ounce (oz) (avoirdupois) =  28.35 g
milligram (mg) =  0.001 g (exact, definition) pound (lb) (avoirdupois) =  0.4535924 kg
kilogram (kg) =  1000 g (exact, definition) ton (short) =  2000 lb (exact, definition)
kilogram (kg) =  2.205 lb ton (short) =  907.185 kg
ton (metric) =  1000 kg (exact, definition) ton (long) =  2240 lb (exact, definition)
ton (metric) =  2204.62 lb ton (long) =  1.016 metric ton
Units of Energy
4.184 joule (J) =  1 thermochemical calorie (cal)
1 thermochemical calorie (cal) =  4.184 × 107  erg
erg =  10–7 J (exact, definition)
electron-volt (eV) =  1.60218 × 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 J[1]
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)
atmosphere (atm) =  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)

1. 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.