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Mass

How much matter is in something. Differs from weight (which is force). SI base: kilogram (kg).

All Mass units (10)

The SI base unit. Defined by Planck's constant since 2019.

1/1000 of a kilogram. Cooking and small packages.

1/1,000,000 kilogram. Medication, trace nutrients.

1000 kilograms. International freight and carbon emissions.

0.453 592 37 kg. US body weight, food packaging.

1/16 of a pound, or about 28.35 g. Cooking in the US.

14 pounds (6.35 kg). UK body weight.

Exactly 64.798 91 milligrams. Bullets, precious metals in troy.

1/1,000,000,000 kilogram. Vitamins, dosage.

200 milligrams. Gemstones.

Popular Mass conversions

kilogram → gram kilogram → milligram kilogram → metric ton kilogram → pound kilogram → ounce kilogram → stone kilogram → grain gram → kilogram gram → milligram gram → metric ton gram → pound gram → ounce gram → stone gram → grain milligram → kilogram milligram → gram milligram → metric ton milligram → pound milligram → ounce milligram → stone milligram → grain metric ton → kilogram metric ton → gram metric ton → milligram metric ton → pound metric ton → ounce metric ton → stone metric ton → grain pound → kilogram pound → gram pound → milligram pound → metric ton pound → ounce pound → stone pound → grain ounce → kilogram ounce → gram ounce → milligram ounce → metric ton ounce → pound ounce → stone ounce → grain stone → kilogram stone → gram stone → milligram stone → metric ton stone → pound stone → ounce stone → grain grain → kilogram grain → gram grain → milligram grain → metric ton grain → pound grain → ounce grain → stone

Frequently Asked Questions

What is the SI base unit of mass?

The SI base mass unit is kg. Most conversions factor through it, except temperature which is affine and fuel-economy which is reciprocal.

Which unit systems are represented?

Mass includes both metric and imperial units (where they exist in this category). For mass and length, both metric (kg, m) and US customary (lb, ft) are listed. For temperature, the three most-common scales (Celsius, Fahrenheit, Kelvin) plus Rankine and Réaumur.

How accurate are these conversions?

Conversions use the standard SI factors (NIST values where applicable). Where two slightly different definitions exist (e.g. KB vs KiB, US vs UK gallon), they are listed as separate units rather than auto-rounded.

Other categories

Distance, height, width — anything that measures how long something is. SI base unit: the metre (m).

How hot or cold something is. Conversions are affine — there is an offset, not just a multiplier.

Size of a 2-D surface. SI base: square metre (m²).

Space occupied by a 3-D object. SI base: litre (L) for everyday use; cubic metre (m³) for SI.

Distance per unit time. SI: metre per second (m/s).

Duration. SI base: the second (s).

Digital information size. SI: the byte (B). Note the difference between decimal (KB=1000) and binary…

Capacity to do work. SI base: joule (J). Also commonly expressed as calories, kWh, BTU.

Force per unit area. SI base: pascal (Pa).

Rotation or turning. SI base: radian (rad).

Distance per unit of fuel, or its reciprocal (fuel per distance). Base: litres per 100 km.