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Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, and other temperature units.

About the Temperature Converter

The Temperature Converter turns a temperature written on one scale into the same temperature on another — Celsius to Fahrenheit for weather and cooking, Celsius to Kelvin for science. Temperature is the one conversion on this site that is not a simple multiplication, because the scales start from different zero points. Type a number, pick the two scales, and the answer updates as you type.

How to convert Celsius to Fahrenheit

Multiply by 9/5, then add 32. The 9/5 is there because a Fahrenheit degree is smaller: 100 Celsius degrees cover the same span as 180 Fahrenheit degrees. The 32 is there because the Fahrenheit scale puts the freezing point of water at 32 rather than 0.

∘F=∘C×95+32∘C=(∘F−32)×59\begin{aligned} ^{\circ}\text{F} &= ^{\circ}\text{C} \times \frac{9}{5} + 32 \\ ^{\circ}\text{C} &= (^{\circ}\text{F} - 32) \times \frac{5}{9} \end{aligned}

Worked example. A warm day of 25 °C is 25 × 1.8 + 32 = 77 °F. Going the other way, an oven at 350 °F is (350 − 32) × 5/9 = 176.7 °C. Order matters — subtract the 32 first, then multiply. Doing it the other way round is the most common error with this conversion.

Celsius to Fahrenheit conversion table

Celsius (°C)Fahrenheit (°F)
-40-40
-20-4
-1014
032
1050
2068
2577
3086
3798.6
40104
50122
100212

How to convert Celsius to Kelvin

Add 273.15. A kelvin and a Celsius degree are exactly the same size, so only the zero point moves — Kelvin starts at absolute zero, the point where thermal motion stops.

  • K = °C + 273.15, and °C = K − 273.15.
  • 0 °C (water freezes) = 273.15 K.
  • 100 °C (water boils at sea level) = 373.15 K.
  • Absolute zero = 0 K = −273.15 °C = −459.67 °F.
  • Kelvin takes no degree sign: write 300 K, not 300 °K.

Real-world values

  • Water freezes at 0 °C, 32 °F, 273.15 K.
  • Normal body temperature is 37 °C, which is 98.6 °F.
  • A comfortable room is 20 °C, which is 68 °F.
  • A hot summer day of 35 °C is 95 °F.
  • A domestic freezer runs at −18 °C, which is −0.4 °F.
  • A moderate oven set to 180 °C is 356 °F.
  • The two scales meet at −40: −40 °C is exactly −40 °F.

Why temperature needs an offset

Every other converter on this site multiplies by a factor, because its units share a zero — zero metres is zero feet. Celsius and Fahrenheit do not share a zero, so their conversion needs a factor and an offset. That is also why you cannot convert a temperature difference with the same formula: a rise of 10 °C is a rise of 18 °F, not 50 °F.

Units this converter supports

Three: Celsius (°C), Fahrenheit (°F) and Kelvin (K). Any pair converts in either direction. The Rankine and Réaumur scales are not offered.

Frequently asked questions

What is the formula to convert Celsius to Fahrenheit?

Multiply by 9/5, which is 1.8, then add 32. So 25 °C becomes 25 × 1.8 + 32 = 77 °F. Body temperature, 37 °C, becomes 98.6 °F.

What is the formula to convert Fahrenheit to Celsius?

Subtract 32 first, then multiply by 5/9. So 100 °F becomes (100 − 32) × 5/9 = 37.78 °C. Doing the two steps in the wrong order is the most common mistake with this conversion.

How do I convert Celsius to Kelvin?

Add 273.15. A degree Celsius and a kelvin are the same size, so only the zero point moves: 0 °C is 273.15 K, and absolute zero is −273.15 °C. Kelvin is written without a degree sign.

Is there a temperature where Celsius and Fahrenheit agree?

Yes, at −40. Minus 40 °C is exactly −40 °F, and it is the only point where the two scales read the same number. It is a quick way to check that a conversion is set up correctly.

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