Temperature Converter
Celsius is used for weather, cooking and science in most of the world, Fahrenheit is the everyday scale in the United States, and Kelvin is the absolute scale used in physics and chemistry. Unlike length or weight, temperature scales don’t just differ by a multiplier — they also start from different zero points, so conversion needs both a scaling and an offset. This converter handles all three scales and refuses impossible inputs below absolute zero (−273.15 °C, 0 K), which can’t physically exist.
How to use the temperature converter
- Enter the temperature.
- Choose the scale it is in and the scale you want.
- Read the result, plus the third scale shown below it.
Formula
°F = °C × 9/5 + 32 and °C = (°F − 32) × 5/9. K = °C + 273.15. The tool converts everything through Celsius, so Fahrenheit to Kelvin is (°F − 32) × 5/9 + 273.15.
Worked examples
Room temperature
20 °C is 68 °F.
A fever threshold
100.4 °F is 38 °C — the usual 38 °C fever line.
Where the scales meet
−40 is the one temperature where Celsius and Fahrenheit agree: −40 °C = -40 °F. Water freezes at 0 °C = 32 °F and boils at 100 °C = 212 °F at sea level.
Temperature reference points
| Event | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20 | 68 | 293.15 |
| Normal body temperature | 37 | 98.6 | 310.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Typical oven for baking | 180 | 356 | 453.15 |
Why the scales are different
Fahrenheit set 0° at the freezing point of a brine mixture and 96° near body temperature, later fixed to water freezing at 32° and boiling at 212°. Celsius set 0° and 100° at water’s freezing and boiling points, and Kelvin is Celsius shifted so that 0 is absolute zero. See also the unit converter hub.
Practice problems
Try these yourself first, then check your answer. The answers come from the calculator above.
- Convert 350 °F (a baking temperature) to Celsius.
Show answer
350 °F in °C: 176.6666667
- Convert 25 °C to Fahrenheit.
Show answer
25 °C in °F: 77
Common mistakes to avoid
- Multiplying by 1.8 but forgetting to add 32 (or subtracting 32 before multiplying). Both parts matter.
- Treating Kelvin as degrees. It is simply “K”, with no degree symbol.
- Using the “double it and add 30” mental shortcut for precise work — it’s only a rough guide for weather.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (1.8) and add 32. For example, 25 °C × 1.8 + 32 = 77 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. For 98.6 °F: (98.6 − 32) × 5/9 = 37 °C.
What is absolute zero?
0 K, or −273.15 °C (−459.67 °F): the lowest possible temperature, where particles have minimum thermal energy.
At what temperature are Celsius and Fahrenheit equal?
At −40, where both scales read the same number.
Why does the US still use Fahrenheit?
It was adopted before the metric system spread and never replaced for everyday weather and cooking, even though science and medicine often use Celsius.
Sources and further reading
Reviewed September 26, 2026 by the SolveCalcPro editorial team. Found a mistake? Tell us; see our editorial policy.