Measures: Temperature — how hot or cold
Kelvin
Temperature counted up from absolute zero.
TemperatureHow it's defined
Since 2019, defined by fixing the Boltzmann constant at exactly 1.380649×10⁻²³ J/K. Its zero is absolute zero — the coldest anything can be — and one kelvin step equals one celsius step; only the starting point differs.
Convert — honestly
-272.15 °C
Degree Celsius · factor exact — exact by definition
-457.87 °F
Degree Fahrenheit · factor exact — exact by definition
Conversions run through the kelvin using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
- Elementii — every melting and boiling point on the element pages ↗ open elementii
- Deep-space instruments and lab physics
Other ways to measure temperature
Source
This page is an authored summary of the authoritative definition — checkable one click away.
NIST — SI Redefinition (2019)