Temperature converter — Celsius, Fahrenheit, Kelvin and more

How to use the temperature converter

1. Enter the reading in Value. Negative temperatures are fine.
2. Pick its scale under From (for example °F).
3. Pick the scale you want under To. The converted reading shows at once.
4. The table under the answer gives the same temperature on all six scales.
5. Tap the swap button to go back the other way.

What it does and when to use it

Most unit changes only need a multiplication. Temperature is different: the scales disagree about both the size of a degree and where zero sits, so every conversion needs a ratio and an offset. That is easy to get wrong in your head, which is why a quick tool helps with recipes from another country, weather forecasts abroad, a child’s fever reading, or science homework that uses kelvin.

The six scales are Celsius (everyday metric), Fahrenheit (everyday use in the United States), Kelvin (science, starting at absolute zero), Rankine (Fahrenheit-sized steps from absolute zero, still met in some US engineering), and two historical scales, Réaumur and Rømer, which turn up in old texts and recipes.

How it works

The tool converts your reading to kelvin, then from kelvin to the target scale:

• K = °C + 273.15
• K = (°F − 32) × 5/9 + 273.15
• K = °R × 5/9
• K = °Ré × 5/4 + 273.15
• K = (°Rø − 7.5) × 40/21 + 273.15

Each formula is reversed for the way out. Because 5/9 does not end in decimal, most results are rounded for display to 12 significant digits.

Worked examples

All three results are from the converter.

Body temperature. 37 °C = 98.6 °F, the number most people know from thermometers.

An American oven setting. 350 °F = 176.666666667 °C. In practice, set a Celsius oven to 175–180 °C.

Room temperature in kelvin. 300 K = 26.85 °C, a warm room. Physics problems often round room temperature to 300 K for this reason.

Useful reference points

Water boils at a lower temperature at altitude, so the 100 °C figure applies at standard sea-level pressure.

Limits and tips

• Readings only, not differences. See the FAQ above for converting a change in temperature.
• Below absolute zero is physically impossible, but the tool does not block it; check your input if you see a negative kelvin value.
• Convert once. For lab work, convert the final figure instead of chaining several conversions, so rounding does not add up.
• Following a recipe from abroad? The volume converter handles cups and millilitres, and the weight converter handles ounces and grams. For travel distances, use the length converter.