Temperature Converter
Convert Celsius, Fahrenheit, Kelvin and Rankine.
25 °C
Celsius
77 °F
Fahrenheit
298.15 K
Kelvin
536.67 °R
Rankine
Formulas from Celsius: °F = °C × 9/5 + 32 · K = °C + 273.15 · °R = (°C + 273.15) × 9/5
Reference points
| Absolute zero | -273.15 °C | -459.67 °F | 0 K |
| Water freezes | 0 °C | 32 °F | 273.15 K |
| Room temperature | 21 °C | 69.8 °F | 294.15 K |
| Body temperature | 37 °C | 98.6 °F | 310.15 K |
| Water boils | 100 °C | 212 °F | 373.15 K |
About Temperature Converter
Temperature is the one everyday conversion that is not a simple multiplication, because Celsius and Fahrenheit disagree about where zero is as well as how big a degree is.
This converter handles all four scales at once, shows the formula it applied, and flags physically impossible values below absolute zero.
How Temperature Converter works in your browser
Temperature scales differ in both the size of a degree and where zero sits, so each conversion needs a scale factor and an offset — Fahrenheit is Celsius × 9 ÷ 5 + 32, and Kelvin is Celsius + 273.15. Rankine is the Fahrenheit-sized absolute scale.
All four scales update together, and the tool warns you if a value falls below absolute zero, which is physically impossible on any scale.
When to use it
- Converting an oven temperature from a recipe written for another country.
- Reading weather forecasts or medical temperatures in an unfamiliar scale.
- Working with Kelvin values in science or engineering coursework.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9, divide by 5, then add 32. So 20 C is 68 F, and 37 C is 98.6 F.
How do I convert Fahrenheit to Celsius?
Subtract 32, multiply by 5, then divide by 9. So 100 F is about 37.8 C.
Why is temperature conversion not a simple ratio?
Celsius and Fahrenheit have different zero points, so conversion needs both a scale factor and an offset.
What is absolute zero?
Minus 273.15 Celsius, or 0 Kelvin - the point where thermal motion is at a minimum. The converter warns if you go below it.
Where do the scales cross?
At minus 40 degrees, Celsius and Fahrenheit read the same number.