Celsius to Fahrenheit Converter

How to convert Celsius to Fahrenheit

To convert Celsius to Fahrenheit, multiply by 9/5 (which is 1.8) and add 32: °F = °C × 1.8 + 32. Going the other way, subtract 32 and divide by 1.8: °C = (°F − 32) × 5/9. The two steps exist because the scales differ in two ways. Their zero points are in different places (water freezes at 0 °C but 32 °F), and their degrees are different sizes: the 100 Celsius degrees between freezing and boiling water span 180 Fahrenheit degrees, a ratio of 180/100 = 9/5.

The converter above works in all directions, including Kelvin, and shows the arithmetic for your number. Kelvin uses Celsius-sized degrees but starts at absolute zero, so K = °C + 273.15.

Worked examples

20 °C to °F: 20 × 1.8 = 36, and 36 + 32 = 68 °F, a comfortable room. 37 °C to °F: 37 × 1.8 = 66.6, plus 32 is 98.6 °F, the classic normal body temperature. 180 °C oven to °F: 180 × 1.8 + 32 = 356 °F, which recipes round to 350 °F. 350 °F to °C: (350 − 32) ÷ 1.8 = 176.7 °C, usually written as 175 or 180 °C.

A quick mental shortcut

For weather, double the Celsius temperature and add 30. 15 °C becomes 60 °F (exact: 59 °F) and 25 °C becomes 80 °F (exact: 77 °F). In reverse, subtract 30 from Fahrenheit and halve it. The shortcut uses 2 instead of 1.8, so the error grows the further you get from about 10 °C: at 40 °C it says 110 °F when the truth is 104 °F. It is good enough to decide on a jacket, not for cooking or medicine. One fixed point worth remembering: −40 is the same in both scales.

Common mistakes

• Adding 32 first. Order matters. For Celsius to Fahrenheit, multiply first, then add 32. For Fahrenheit to Celsius, subtract 32 first, then divide.
• Converting a temperature difference like a temperature. A rise of 10 °C is a rise of 18 °F, not 50 °F. Differences scale by 1.8 only; the +32 applies to readings, not changes.
• Writing "degrees Kelvin". Kelvin has no degree sign: 300 K, not 300 °K.

When the conversion is misleading

The formula is exact, but the inputs often are not. Oven dials are typically off by 10–25 °F, so converting a recipe to the decimal place is false precision; round to the nearest 5 or 10 degrees. Body temperatures vary by person, time of day and where they are measured, so 37 °C / 98.6 °F is an average, not a cutoff. For more number conversions, see the scientific notation calculator and the decimal to fraction calculator.