This temperature converter converts between Fahrenheit, Celsius and Kelvin instantly — edit any field and the other two follow. The scale everyone forgets the formula for, handled.
Type in any box. Kelvin is the scientists’ scale: it starts at absolute zero (−273.15 °C), the coldest possible temperature, and uses Celsius-sized degrees — so it is written without a degree symbol, just “K”.
The Formulas
- °C = (°F − 32) × 5/9 — subtract first, then scale; order matters
- °F = °C × 9/5 + 32
- K = °C + 273.15
- Mental shortcut for weather: °F → °C, subtract 30 and halve (100°F → ~35 °C; exact answer 37.8). Close enough to decide on a jacket, wrong enough to ruin a lab.
The scales meet at exactly one point: −40° is −40° in both Fahrenheit and Celsius — a fact that wins bets and anchors sanity checks. This converter is part of our Conversion Calculators collection.
Reference Points Worth Memorizing
| Point | °F | °C | K |
|---|---|---|---|
| Absolute zero | −459.67 | −273.15 | 0 |
| Water freezes | 32 | 0 | 273.15 |
| Room temperature | 68–72 | 20–22 | 293–295 |
| Human body | 98.6 | 37 | 310.15 |
| Fever threshold | 100.4 | 38 | 311.15 |
| Water boils (sea level) | 212 | 100 | 373.15 |
| Oven: moderate | 350 | 177 | 450 |
| Oven: pizza-hot | 500 | 260 | 533 |
Why Three Scales Exist
Fahrenheit (1714) was calibrated to brine, ice and body temperature — surprisingly weather-friendly granularity. Celsius (1742) keys everything to water: 0 freezes, 100 boils. Kelvin (1848) starts where thermal motion stops, making it the only scale where equations of physics work without offsets (you cannot take a ratio in Celsius — 20 °C is not “twice as hot” as 10 °C; 293 K genuinely is nearly twice 283 K in thermal terms). Weather in the US speaks Fahrenheit, kitchens split by ocean, and science speaks Kelvin.
Related Tools
- Conversion Calculators — the full collection
- Dew Point Calculator — temperature meeting humidity
Frequently Asked Questions
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. 100°F → (68) × 5/9 = 37.78 °C. In reverse: multiply by 9/5 and add 32.
What is 37 degrees Celsius in Fahrenheit?
98.6°F — normal human body temperature, which is why 37 °C appears on every imported thermometer.
Where do Fahrenheit and Celsius meet?
At −40: −40°F = −40°C exactly, the unique solution of the two formulas set equal.
Why does Kelvin have no degree symbol?
Kelvin is an absolute unit (like a meter), not a relative degree — the SI convention writes 310 K, not 310°K. Its zero is a physical floor, not an arbitrary marker.
Can temperature go below 0 Kelvin?
No — 0 K is absolute zero, where thermal motion is minimal. Exotic lab systems flirt with “negative temperature” statistics, but they are actually hotter than infinite temperature, not colder than zero.
Is this temperature converter free?
Yes — free, instant, no sign-up, live conversion as you type.