Temperature Converter — Celsius to Fahrenheit, Kelvin & More
Convert temperature units online free — Celsius to Fahrenheit, Fahrenheit to Celsius, Kelvin, Rankine and more. The conversion formula is shown so you can understand the calculation.
Last updated: June 2026
Reference points
- Water freezes
- 0 °C · 32 °F · 273.15 K
- Body temperature
- 37 °C · 98.6 °F · 310.15 K
- Water boils
- 100 °C · 212 °F · 373.15 K
About this tool
Every temperature scale, side by side
Temperature is one of the trickiest conversions because the scales don't share a zero — water freezes at 0 °C but 32 °F, and Kelvin begins at absolute zero. This temperature converter takes the arithmetic off your hands: type a value into any of the four scales and Celsius, Fahrenheit, Kelvin and Rankine all update at the same instant.
The two everyday scales are Celsius (used by most of the world and in science) and Fahrenheit (used in the United States), related by °F = °C × 9/5 + 32. For scientific and engineering work, Kelvin is the SI absolute scale starting at absolute zero with Celsius-sized steps, and Rankine is the absolute scale built on Fahrenheit-sized degrees.
To help you sanity-check a result, the converter lists familiar reference points — the freezing and boiling points of water and normal body temperature — across all the scales. Whether you're converting a weather forecast, a cooking temperature, a fever reading or a physics problem, the answer appears instantly. Everything runs in your browser, so it's private, free and available whenever you need it.
How it works
Three quick steps — no account, nothing uploaded to a server.
Type a temperature
Enter a value in Celsius, Fahrenheit, Kelvin or Rankine.
See all scales
The other three scales convert at the same instant.
Check the references
Compare against freezing, body temp and boiling points.
FAQ
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32: °F = (°C × 9/5) + 32. So 25 °C is (25 × 1.8) + 32 = 77 °F. Type into the Celsius box and the Fahrenheit box updates instantly using exactly this formula.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9: °C = (°F − 32) × 5/9. For example, 98.6 °F is (98.6 − 32) × 5/9 = 37 °C, normal body temperature. The converter does this automatically when you type in the Fahrenheit box.
What is Kelvin and when is it used?
Kelvin is the SI base unit of temperature, used in science. It starts at absolute zero (0 K = −273.15 °C), the coldest possible temperature, and shares the same step size as Celsius — so a change of 1 K equals a change of 1 °C. To convert, add 273.15 to Celsius.
What is Rankine?
Rankine is an absolute temperature scale, like Kelvin, but using Fahrenheit-sized degrees. Zero Rankine is absolute zero, and 0 °F equals 459.67 °R. It's used in some US engineering and thermodynamics work; the converter handles it alongside the other three scales.
What is absolute zero?
Absolute zero is the lowest possible temperature, where particles have minimal motion: 0 K, which is −273.15 °C or −459.67 °F. Nothing can be colder. Enter −273.15 in the Celsius box to see it line up at 0 in the Kelvin box.
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