gram
gmass · International · Modern
1 g = 0.001 kg.
Converter
mass · Historical gemstone trade · Pre-20th-century; locality-dependent
old carat / pre-metric carat
variant
- Record
- M555
- Definition quality
- Variant-dependent
- Conversion mode
- variant selection
- Calculator
- Variant selection required
Definition
Historical carats were not globally uniform. U.S. NBS material gives one old-carats conversion basis of 205.3 mg; French and other historical standards differed.
Reference value by variant
old carat / pre-metric carat covers several documented traditions, each with its own value. Choose a variant below to see a figure.
History & use
Standardization solved a real trade problem: famous historical gemstones are often described in carats that are not today's metric carat.
Modern use
Modern use is context-dependent and varies by region or measurement system.
Sources & evidence
Source tier — · confidence high
Related measurements
kilogram
kgmass · International · Modern
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.
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.
variant