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Freezing and Boiling Points Across All Temperature Scales

June 23, 2025 โ€ข 4 min read

Water freezes and boils at specific temperatures โ€” but what those numbers look like depends entirely on which scale you use. Here is a comparison across every major temperature scale, plus the history behind how each one was defined.

The Four Main Temperature Scales

Freezing point of water:

0ยฐC | 32ยฐF | 273.15 K | 491.67ยฐR

Boiling point of water:

100ยฐC | 212ยฐF | 373.15 K | 671.67ยฐR

Celsius (Centigrade)

Created by Anders Celsius in 1742. Originally, his scale was inverted (100ยฐ for freezing, 0ยฐ for boiling), but it was reversed after his death. The scale is defined by water: 0ยฐ = freezing, 100ยฐ = boiling at standard atmospheric pressure.

  • โ–ถ Degree size: 1/100 of the range between freezing and boiling
  • โ–ถ Used by: nearly every country worldwide
  • โ–ถ Best for: everyday life, weather, cooking

Fahrenheit

Created by Daniel Fahrenheit in 1724. He set 0ยฐ at the coldest temperature he could create (ice, water, and ammonium chloride mixture), and originally set 96ยฐ as body temperature. Water freezing ended up at 32ยฐ and boiling at 212ยฐ.

  • โ–ถ Degree size: 1/180 of the range between freezing and boiling (smaller than Celsius degrees)
  • โ–ถ Used by: United States, Liberia, Myanmar, some Caribbean nations
  • โ–ถ Best for: weather reporting in the US (the 0-100ยฐF range covers most habitable weather)

Kelvin

Proposed by Lord Kelvin (William Thomson) in 1848. Uses the same degree size as Celsius but starts at absolute zero (-273.15ยฐC). There are no negative Kelvin values.

  • โ–ถ Degree size: same as Celsius
  • โ–ถ Used by: scientists, engineers, physicists worldwide
  • โ–ถ Best for: thermodynamics, gas laws, colour temperature

Rankine

Created by William Rankine in 1859. Uses the same degree size as Fahrenheit but starts at absolute zero (-459.67ยฐF). It is the Fahrenheit equivalent of Kelvin.

  • โ–ถ Degree size: same as Fahrenheit
  • โ–ถ Used by: some US engineering applications (steam tables, HVAC)
  • โ–ถ Best for: thermodynamic calculations when working in imperial units

Conversion Formulas

  • โ–ถ ยฐC to ยฐF: (ยฐC ร— 9/5) + 32
  • โ–ถ ยฐF to ยฐC: (ยฐF - 32) ร— 5/9
  • โ–ถ ยฐC to K: ยฐC + 273.15
  • โ–ถ ยฐF to ยฐR: ยฐF + 459.67
  • โ–ถ K to ยฐR: K ร— 9/5

One interesting crossover: -40 is the same in both Celsius and Fahrenheit. It is the only point where the two scales intersect.

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