Celsius to Fahrenheit Converter (°C to °F)

The Celsius to Fahrenheit formula

To convert °C to °F, multiply the Celsius temperature by 9/5 (which is the same as 1.8) and then add 32:

°F = °C × 9/5 + 32

Worked example: for 25 °C, first multiply: 25 × 9/5 = 45. Then add 32: 45 + 32 = 77. So 25 °C is 77 °F. The order matters — always multiply first, then add. If you add 32 first you will get a badly wrong answer.

Going the other way, subtract 32 first and then multiply by 5/9: °C = (°F − 32) × 5/9. Our Fahrenheit to Celsius converter walks through that direction with recipe and weather examples.

For science work you may also need Kelvin (K = °C + 273.15) or Rankine (°R = °F + 459.67). The converter above shows both automatically, and the Kelvin converter explains them in more depth.

For more worked examples and an explanation of each step, see the Celsius to Fahrenheit formula guide.

Mental shortcut: double it and add 30

When you only need a rough idea — reading a weather forecast abroad, for example — double the Celsius number and add 30. It is easy to do in your head because doubling is simpler than multiplying by 1.8, and 30 is a rounder number than 32.

The trick is exact at 10 °C and drifts the further you move away. Around everyday weather temperatures it is within a few degrees, which is fine for deciding whether to take a jacket. It is not good enough for cooking, medicine or lab work, where you should use the exact formula.

A slightly better version: double it, subtract 10%, then add 32. For 30 °C that gives 60 − 6 + 32 = 86 °F, which is exactly right, because doubling and removing a tenth is the same as multiplying by 1.8.

Popular Celsius to Fahrenheit conversions

These are the values people look up most often, from oven settings in recipes to body temperature and the weather.

• 180 °C = 356 °FModerate oven
• 200 °C = 392 °FHot oven
• 220 °C = 428 °FVery hot oven
• 37 °C = 98.6 °F37 °C conversion
• 0 °C = 32 °FWater freezes
• 100 °C = 212 °FWater boils (sea level)
• −40 °C = −40 °FWhere both scales meet
• 30 °C = 86 °FHot summer day
• 40 °C = 104 °FHeatwave
• 25 °C = 77 °FWarm room

Baking? Fan ovens and gas marks change the numbers again — see the oven temperature conversion guide for fan, conventional and air fryer settings.

Celsius to Fahrenheit chart

A quick reference from −40 °C to 100 °C. Each 5 °C step adds exactly 9 °F, which is a handy pattern to remember: 5 Celsius degrees are always 9 Fahrenheit degrees.

Need every single degree, below-zero values or a version to print? The full printable Celsius to Fahrenheit chart covers −50 °C to 150 °C.

Celsius vs Fahrenheit: what is the difference?

Both scales measure the same thing, but they start at different points and use different-sized degrees. On the Celsius scale, pure water freezes at 0 °C and boils at 100 °C at sea level, so there are 100 steps between the two. On the Fahrenheit scale the same two points are 32 °F and 212 °F — 180 steps apart.

Why add 32, and why 9/5?

The 32 is there because the freezing point of water sits at 32 on the Fahrenheit scale instead of 0. The 9/5 comes from the ratio of the two ranges: 180 Fahrenheit degrees cover the same gap as 100 Celsius degrees, and 180 ÷ 100 = 1.8 = 9/5. So each Celsius degree is 1.8 times bigger than a Fahrenheit degree.

Converting a temperature difference

One detail catches many people out. If you are converting a change in temperature — “the oven is 10 °C hotter” or “the forecast dropped by 5 °C” — you multiply by 1.8 only. You do not add 32. A rise of 10 °C is a rise of 18 °F, not 50 °F. The 32 belongs to a reading on the thermometer, not to a gap between two readings. In short: 1 °C of change equals 1.8 °F of change.

Which countries use Fahrenheit?

The United States uses Fahrenheit for daily life — weather, cooking and body temperature — along with a handful of smaller places such as some Caribbean and Pacific territories. Almost everywhere else uses Celsius. Canada and the United Kingdom are officially Celsius, but you will still see Fahrenheit in everyday life there: many ovens, older recipes and imported appliances show °F, and some people still talk about summer heat in Fahrenheit.