Temperature Converter
Convert any temperature between Celsius, Fahrenheit, Kelvin and Rankine, with the formulas and a handy reference chart.
All units
🔒 Runs entirely in your browser. Nothing you enter is sent to a server.
Temperature is the one unit conversion you can’t do just by multiplying. The Celsius and Fahrenheit scales start from different zero points, so every conversion needs both a multiplication and an offset. This tool handles that for you between Celsius, Fahrenheit, Kelvin and the less common Rankine scale, and shows all four at once.
How to use the temperature converter
- Type a temperature into Value. Negative numbers work too.
- Pick the scale you have in From and the one you want in To.
- Read the result, or check the table to see every scale together.
Temperature conversion formulas
| From → To | Formula |
|---|---|
| Celsius → Fahrenheit | °F = °C × 9/5 + 32 |
| Fahrenheit → Celsius | °C = (°F − 32) × 5/9 |
| Celsius → Kelvin | K = °C + 273.15 |
| Kelvin → Celsius | °C = K − 273.15 |
| Fahrenheit → Kelvin | K = (°F − 32) × 5/9 + 273.15 |
| Celsius → Rankine | °R = (°C + 273.15) × 9/5 |
Quick reference chart
| What | Celsius | Fahrenheit |
|---|---|---|
| Water freezes | 0°C | 32°F |
| Cool room | 18°C | 64.4°F |
| Comfortable room | 21°C | 69.8°F |
| Normal body temperature | 37°C | 98.6°F |
| Fever | 38°C | 100.4°F |
| Hot summer day | 35°C | 95°F |
| Water boils (sea level) | 100°C | 212°F |
| Moderate oven | 180°C | 356°F (recipes say 350°F) |
| Hot oven | 220°C | 428°F (recipes say 425°F) |
Mental math for travelers
- °C → °F (rough): double it and add 30. So 25°C becomes 80°F (exact: 77°F). This is close enough to decide whether you need a jacket.
- °F → °C (rough): subtract 30 and halve it. So 70°F becomes 20°C (exact: 21.1°C).
- Remember a few anchors: 10°C = 50°F, 20°C = 68°F, 30°C = 86°F. Each 10°C step adds 18°F.
These shortcuts drift further from the true value at extreme temperatures, so use the converter for cooking, science or medicine.
Which countries use Fahrenheit?
Only a handful still use Fahrenheit for everyday weather: the United States and a few of its territories, plus some Caribbean and Pacific nations. Most of the world uses Celsius. Scientists everywhere work in Celsius and Kelvin. That is why the conversion matters so often when you read recipes, oven dials, weather forecasts or medical advice from abroad.
Frequently asked questions
What is the formula to convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8) and add 32. For example, 20°C × 1.8 + 32 = 68°F.
What is the formula to convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature, then multiply by 5/9. For example, (100°F − 32) × 5/9 ≈ 37.8°C.
At what temperature are Celsius and Fahrenheit equal?
At −40 degrees. −40°C is exactly −40°F, the only point where the two scales meet.
Why can't Kelvin be negative?
Kelvin starts at absolute zero (−273.15°C), the lowest temperature physically possible, where particles have the least possible energy. Nothing can be colder, so there are no negative Kelvin temperatures. Kelvin is also written without the degree sign.