🌡️ Temperature Converter
Celsius, Fahrenheit, and Kelvin. Runs privately in your browser.
Three scales, three different zero points
The three scales have different zero points and different degrees: Celsius and Kelvin share step size but shift by 273.15; Fahrenheit uses 180 steps per 100 °C, hence the 5/9 ratio. Conversions must handle both the offset and the scale — this is why temperature, unlike length or weight, cannot be converted by a single multiplication.
Kelvin is the scientific absolute scale: 0 K is absolute zero, and there are no negative Kelvins. If a result below 0 K appears, the input was physically impossible — the converter will happily display nonsense if you feed it nonsense, so sanity-check inputs near the extremes.Rounding conventions matter in cooking and weather. Oven conversions round to the nearest 10 degrees (350 °F ≈ 175 °C, marked as 180 on UK dials); weather reports round to whole degrees. The converter preserves full precision precisely so you can apply the right rounding for your context — precision first, then round deliberately, not the reverse.
C → F: ×9/5 + 32. F → C: −32, ×5/9. C → K: +273.15. The converter converts source → Celsius → target.
Body temperature and a 350 °F oven
37 °C body temperature: 37 × 9/5 + 32 = 98.6 °F, or 310.15 K. A 350 °F oven: (350 − 32) × 5/9 ≈ 176.7 °C — the '180 °C' on UK recipes. Absolute zero, −273.15 °C, is exactly 0 K.
Half-finished conversions
- Adding only the 32 offset without the 5/9 factor, or vice versa — the two-part conversion is where hand maths fails.
- Forgetting the 273.15 (writing +273 or −273) in Kelvin work.
- Expecting a linear 'multiply by 1.8' shortcut to work in reverse without the 32 offset.
- Reporting sub-zero Kelvin results from bad inputs instead of catching them.Converting 'room temperature' across systems without rounding — 21 °C is 69.8 °F, which no one quotes; round to 70 °F.
Temperature questions
What's the formula for Celsius to Fahrenheit?
Multiply by 9/5 and add 32. 20 °C → 68 °F. The calculator does it exactly.
At what temperature do Celsius and Fahrenheit match?
−40°. Both scales read −40 at the same physical temperature.
Why does Kelvin exist?
It starts at absolute zero, so it's proportional to thermal energy — required in physics formulas like the ideal gas law.
Is −40 C really the same as −40 F?
Yes — the crossover point. Below it, Fahrenheit numbers run colder than Celsius.
What is 98.6 F in Celsius?
(98.6 − 32) × 5/9 = 37 °C — normal body temperature.
What is 180 C in Fahrenheit for baking?
180 × 9/5 + 32 = 356 °F — most recipes round the dial to 350.
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Tip: double-check inputs before relying on results for important decisions.