Thermodynamic scale based on 2 fixed points:

- Absolute zero
- Triple point of water – ice, water, water vapor coexist in equilibrium – convenient and easily reproducible, 0.01°C and 611.73 Pa

$T_{c} = T – 273.15$, where $T_{c}$ is in Celsius scale, T is in Kelvin scale.

Thermodynamic scale is shifted so that we can conveniently compare the experimental value with the true value.