Convert Celsius to Fahrenheit
Convert Celsius (°C) to Fahrenheit (°F) instantly, with the exact formula and the reference points worth memorizing.
- Celsius (°C)1
- Fahrenheit (°F)33.8
- Kelvin (K)274.15
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The Celsius to Fahrenheit formula
To convert Celsius to Fahrenheit, use °F = °C × 9/5 + 32. Multiply the Celsius value by 1.8 (that's 9/5), then add 32. For example, 25°C becomes 25 × 1.8 = 45, plus 32 = 77°F. Order matters: multiply first, add second — adding 32 before you multiply gives the wrong answer. Need a quick estimate in your head? "Double it and add 30" gets you close (20°C is about 70°F; the exact value is 68°F), which is plenty accurate for checking the weather.
Reference temperatures worth knowing
Water freezes at 0°C = 32°F and boils at 100°C = 212°F. Normal body temperature, 37°C, works out to exactly 98.6°F — the number US clinics watch for fevers. A comfortable room at 20°C is 68°F, a hot summer day at 30°C is 86°F, and a common baking oven at 180°C is 356°F. One curiosity: -40°C and -40°F are the same value, the single point where both scales meet. Memorize a few of these and you can eyeball almost any reading.
When you need it & common mistakes
Fahrenheit is the everyday standard in the United States, so you'll convert it for US weather forecasts, oven temperatures in recipes, thermostat and water-heater settings, and thermometer readings while traveling. The most common mistake is adding 32 to a temperature difference. Temperature is affine — it carries a +32 offset, so it isn't a simple proportion — but a change of 1°C equals a change of only 1.8°F. If it warms up 5°C, that's 9°F warmer, not 41°F. Round to fit the context.
Frequently asked questions
What is 37°C in Fahrenheit?
37 × 9/5 + 32 = 98.6°F. That's the familiar "normal" body temperature; in the US, 98.6°F is the baseline, and anything above about 38°C (100.4°F) is generally treated as a fever.
Is there a temperature where Celsius and Fahrenheit are equal?
Yes — at -40 degrees. -40°C = -40°F is the one point where both scales read the same. Plug it in: -40 × 1.8 = -72, then +32 = -40.
Why can't I just multiply — why add 32?
Because the two scales put their zero in different places. Water freezes at 0° Celsius but 32° Fahrenheit, so you first stretch the scale by 1.8 and then shift it up by 32. That +32 offset is why temperature isn't a simple proportion and multiplying alone won't give the right answer.