gram
gmass · International · Modern
1 g = 0.001 kg.
Converter
mass · International · Modern
kilogram
kgexact
- Record
- M009
- Definition quality
- Standardized
- Conversion mode
- multiplicative
- Calculator
- Fully calculable
None identified for current SI definition; name etymology not researched in this batch.
Definition
SI base unit of mass. The Planck constant is fixed exactly at 6.62607015×10^-34 J·s, which defines the kilogram through the metre and second.
Reference value
One kilogram is equal to 1 kilogram.
History & use
Early metric mass standards were linked to water. From 1889 the kilogram was defined by the International Prototype Kilogram; in 2019 the artifact definition was replaced by one based on the Planck constant.
Modern use
International SI base unit for mass.
Did you know?
The kilogram was the last SI base unit to be defined by a unique physical artifact before the 2019 revision.
Sources & evidence
Source tier Tier A · confidence High
- Definition Source — https://www.bipm.org/en/measurement-units/si-defining-constants
- History Source — https://www.nist.gov/nist-museum/defining-international-system-units-si
- Modern Use Source — https://www.bipm.org/en/measurement-units/si-base-units
- Trivia Source — https://www.nist.gov/si-redefinition/kilogram-introduction
Related measurements
mass · International · Modern
1 tonne = 1000 kg.
mass · UK / US · Modern / historical
1 avoirdupois ounce = exactly 1/16 international pound = 0.028349523125 kg.
mass · UK / US · Modern / historical
1 international avoirdupois pound = exactly 0.45359237 kg.
stone
stmass · UK / US · Modern / historical
1 stone = 14 lb = exactly 6.35029318 kg using the international pound.
mass · International · Modern
Dalton/u is 1/12 of the mass of a free carbon-12 atom in its ground state. CODATA 2022: 1.66053906892(52)×10^-27 kg.
approx.mass · Ancient Greece / Rome · Antiquity
Greek talent was not one universal standard.
variantmass · Ancient Greece / Rome · Antiquity
Modern scholarship cautions that proposed SI values span roughly 322.56–330 g.
approx.