-20 degrees Celsius
-20 °CTemperature · definition
Celsius and Fahrenheit have shifted zero points. Differences are useful; “twice as hot” in °C or °F is not a physical temperature ratio.
Temperature
Just how hot is -20 degrees Celsius?
Below freezing
-20 °C
-20 degrees Celsius
Celsius and Fahrenheit have shifted zero points.
-20 °CTemperature
0 K · absolute zero
Water triple point
The water triple point is the unique temperature and pressure at which water can exist simultaneously as solid, liquid, and vapour in equilibrium.
0.01 °CTriple-point temperature
0 K · absolute zero
Celsius and Fahrenheit zero points are offsets. Compare temperature differences, not ratios in °C or °F. The kelvin axis starts at absolute zero.
A little perspective
-20 degrees Celsius is 20.01 K lower than the water triple point.
Measurements, assumptions & sources +
-20 degrees Celsius
Temperature: -20 °C; definition.
Celsius and Fahrenheit have shifted zero points. Differences are useful; “twice as hot” in °C or °F is not a physical temperature ratio.
Water triple point
Triple-point temperature: 0.01 °C; specified.
The triple point of water is 273.16 K for a specified isotopic composition at its equilibrium pressure. It is distinct from ordinary freezing water at atmospheric pressure.
IAPWS — Fundamental physical constants of water
The marked triple-point temperature is calibrated. Unmeasured illustration details are representative.
Measurement details
Why these numbers?
Compare -20 degrees Celsius with the water triple point. The notes below explain how each value was chosen.
Water triple point
0.01 °CTriple-point temperature · specified
The triple point of water is 273.16 K for a specified isotopic composition at its equilibrium pressure. It is distinct from ordinary freezing water at atmospheric pressure.
- Comparing
- Temperature ↔ Triple-point temperature
- Relative size
- We compare temperatures using a difference in kelvins, not a ratio.
How to read the visual
The diagram uses the recorded measurements. Details outside the marked spans do not set the scale.
Compare temperature differences in kelvins; Celsius and Fahrenheit ratios are not meaningful.
-4 °Fdegrees Fahrenheit
253.15 Kkelvin
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