Measures: Mass — how much stuff
Kilogram
The base unit of mass — a litre of water, near enough.
MassHow it's defined
Until 2019 the kilogram was a physical platinum-iridium cylinder in a vault near Paris — the last artifact unit. It is now defined by fixing the Planck constant at exactly 6.62607015×10⁻³⁴ J·s, so it can be realized by any equipped lab on Earth.
Convert — honestly
1000 g
Gram · factor exact — exact by definition
0.001 t
Tonne · factor exact — exact by definition
2.20462262 lb
Pound · factor exact — exact by the 1959 agreement
6.0221e+26 u
Atomic mass unit · factor measured — measured (CODATA), carries uncertainty
Conversions run through the kilogram using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
- Inventorii — stock weights ↗ open inventorii
- Gym plates and grocery scales across most of the world
Other ways to measure mass
Source
This page is an authored summary of the authoritative definition — checkable one click away.
NIST — SI Redefinition (2019)