Why are there so many scales?

Celsius, Fahrenheit and Kelvin are the everyday and scientific standards; Rankine is Kelvin's Fahrenheit-based sibling; Delisle, Newton, Réaumur and Rømer are historical European scales you meet in old records and period instruments.

Why can temperature go negative in some scales but not Kelvin?

Kelvin is absolute — 0 K is the physical floor — while Celsius and Fahrenheit place zero at convenient reference points (freezing water, brine). Negative degrees just mean "below that reference", not "less than no heat".

Which scale should I use in code?

Kelvin for physics and thermodynamics (ratios are meaningful), Celsius or Fahrenheit for user-facing display. Converting at the boundary once is cheaper than mixing scales through your logic.

Temperature converter — Guide

Degrees temperature conversions for Kelvin, Celsius, Fahrenheit, Rankine, Delisle, Newton, Réaumur, and Rømer.

What it is and when to use it

Convert a temperature across eight scales at once: Celsius, Fahrenheit, Kelvin, Rankine, Delisle, Newton, Réaumur and Rømer. Type a value on any scale and the others update live — whether you are checking an oven setting from a European recipe or decoding historical scientific data that used Réaumur.

Converts between Celsius, Fahrenheit, Kelvin and other temperature scales.

How to use it

Enter a value on any scale
The other scales update automatically
Copy the result you need

A worked example

Fill in a sample temperature

Copy this into the tool, or open Temperature converter

Questions people ask

Why are there so many scales?: Celsius, Fahrenheit and Kelvin are the everyday and scientific standards; Rankine is Kelvin's Fahrenheit-based sibling; Delisle, Newton, Réaumur and Rømer are historical European scales you meet in old records and period instruments.
Why can temperature go negative in some scales but not Kelvin?: Kelvin is absolute — 0 K is the physical floor — while Celsius and Fahrenheit place zero at convenient reference points (freezing water, brine). Negative degrees just mean "below that reference", not "less than no heat".
Which scale should I use in code?: Kelvin for physics and thermodynamics (ratios are meaningful), Celsius or Fahrenheit for user-facing display. Converting at the boundary once is cheaper than mixing scales through your logic.

Next steps

Open the Temperature converter tool

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