International System of Units (SI)

Base units

unit abbreviation physical quantity

metre m length

second s time

kilogram kg mass

ampere A electric current

kelvin K thermodynamic temperature

candela cd luminous intensity

mole mol amount of substance

Length

unit abbreviation number of metres approximate U.S. equivalent

kilometre km 1,000 0.62 mile

centimetre cm 0.01 0.39 inch

millimetre mm 0.001 0.039 inch

micrometre μm 0.000001 0.000039 inch

nanometre nm 0.000000001 0.000000039 inch

Area

unit abbreviation number of square metres approximate U.S. equivalent

square kilometre sq km, or km² 1,000,000 0.3861 square mile

hectare ha 10,000 2.47 acres

are a 100 119.60 square yards

square centimetre sq cm, or cm² 0.0001 0.155 square inch

Volume

unit abbreviation number of cubic metres approximate U.S. equivalent

cubic metre m³ 1 1.307 cubic yards

cubic centimetre cu cm, cm³, or cc 0.000001 0.061 cubic inch

Capacity

unit abbreviation number of litres approximate U.S. equivalent

kilolitre kl 1,000 1.31 cubic yards

litre l 1 61.02 cubic inches

centilitre cl 0.01 0.61 cubic inch

millilitre ml 0.001 0.061 cubic inch

microlitre μl 0.000001 0.000061 cubic inch

Mass and weight

unit abbreviation number of grams approximate U.S. equivalent

metric ton t 1,000,000 1.102 short tons

gram g 1 0.035 ounce

centigram cg 0.01 0.154 grain

milligram mg 0.001 0.015 grain

microgram μg 0.000001 0.000015 grain

Energy

unit symbol physical quantity expressed in base units

hertz Hz frequency 1/s

newton N force, weight (m × kg)/s²

joule J work, energy, quantity of heat (m² × kg)/s²

pascal Pa pressure, stress kg/(m × s²)

watt W power (m² × kg)/s³

coulomb C electric charge s × A

volt V electric potential difference (m² × kg)/(s³ × A)

farad F electric capacitance (s² × s² × A²)/(m² × kg)

ohm Ω electric resistance, reactance (m² × kg)/(s³ × A²)

siemens S electric conductance (s³ × A²)/(m² × kg)

weber Wb magnetic flux (m² × kg)/(s² × A)

tesla T magnetic induction kg/(s² × A)

henry H inductance (m² × kg)/(s² × A²)

lumen lm luminous flux cd × sr

lux lx illuminance (cd × sr)/m²