Temperature Converter

Type a number, pick your scales, and read the result alongside the formula used

Enter any temperature in the input field — positive, negative, or decimal — then choose the scale you are converting from and the scale you want. The result appears immediately without pressing any button. The formula used for that specific pair of scales is shown directly below the result, so you can check the working yourself rather than trusting a number with no explanation. The tool covers five scales: Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. For most everyday use, Celsius to Fahrenheit is the pair you need. Kelvin matters when you're doing thermodynamic calculations where negative values make no physical sense, since it starts at absolute zero.

The scale reference cards and the quick mental-maths tip

Below the converter, each scale has a reference card listing its freezing point, boiling point, and — for Kelvin and Rankine — the absolute zero value in that scale's units. There is also a quick-estimate tip for rough mental arithmetic: doubling the Celsius value and adding 30 gives an approximate Fahrenheit figure, close enough for weather and body-temperature checks. The Réaumur card is there for completeness — you'll only need it if you're working with older European scientific texts where that scale occasionally appears.