What is Temperature Conversion?
The world measures temperature on three scales. Celsius (°C) is used by nearly every country for weather, cooking, and science. Fahrenheit (°F) remains the everyday scale in the United States. Kelvin (K) is the SI base unit used in physics and chemistry — it starts at absolute zero, the coldest temperature possible. Converting between them is a constant small chore: reading a US recipe in Europe, checking American weather, or working through a physics problem.
What Does This Tool Do?
Enter a temperature, pick the source and target scales, and the converted value appears instantly — along with a table showing the same temperature in all three scales at once. The swap button (⇄) reverses the direction in one click, and your unit choices are remembered for the next visit.
How to Use This Tool
- Type the temperature value.
- Choose the scale you’re converting from and to.
- Read the result — it updates as you type. Copy it with one click.
- Use ⇄ to flip the conversion direction.
The Conversion Formulas
| Conversion | Formula |
|---|---|
| °C → °F | multiply by 9/5, then add 32 |
| °F → °C | subtract 32, then multiply by 5/9 |
| °C → K | add 273.15 |
| K → °C | subtract 273.15 |
| °F → K | convert to °C first, then add 273.15 |
A handy mental shortcut for °C → °F: double it and add 30. It’s exact at 10°C (50°F) and stays within a couple of degrees across the everyday weather range.
Reference Points Worth Memorizing
| °C | °F | K | |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Scales cross | −40 | −40 | 233.15 |
| Water freezes | 0 | 32 | 273.15 |
| Cool room | 18 | 64.4 | 291.15 |
| Room temperature | 21 | 69.8 | 294.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Hot summer day | 35 | 95 | 308.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Oven, moderate | 180 | 356 | 453.15 |
| Oven, hot | 220 | 428 | 493.15 |
Why −40 is Special
The Celsius and Fahrenheit scales intersect at exactly −40: the only temperature that reads the same on both. It falls straight out of the formulas — solving F = 9C/5 + 32 with F = C gives −40. It’s also a great sanity check: type −40 into this converter and both scales should agree.
Popular Conversions
Dedicated pages with formulas, tables, and shortcuts for the pairs people look up most: Celsius to Fahrenheit and Fahrenheit to Celsius.
Frequently Asked Questions
Is my data private?
Yes — the conversion runs entirely in your browser. Nothing you type is sent anywhere, and the tool works offline once loaded.
Why does Kelvin have no degree symbol?
Kelvin is an absolute scale — its zero is physically meaningful (no thermal energy), not an arbitrary reference like water’s freezing point. By SI convention, absolute units drop the degree sign: you write 300 K, not 300°K.
What's the quick way to convert oven temperatures?
Common oven equivalences: 160°C ≈ 325°F, 180°C ≈ 350°F, 200°C ≈ 400°F, 220°C ≈ 425°F. Recipes tolerate small differences, so these rounded pairs are what cookbooks themselves use. For fan (convection) ovens, reduce the Celsius figure by about 20°.
Why is US body temperature quoted as 98.6°F?
It’s the Fahrenheit conversion of 37°C, a 19th-century average measured in Celsius and converted with misleading precision. Modern studies put typical body temperature slightly lower and varying through the day — so don’t read the .6 as medical exactness.
Can a temperature be below 0 K?
Not in the classical sense — 0 K (−273.15°C) is absolute zero, where particles have minimal motion. This converter accepts any number mathematically, but physically, negative Kelvin readings indicate an input error.