Celsius to Fahrenheit
Convert Celsius to Fahrenheit and Kelvin instantly with the exact formula.
Formula
°F = °C × 9/5 + 32. The boiling point of water is 100 °C = 212 °F.
Celsius is the metric temperature scale used by almost every country in the world. Fahrenheit remains the standard in the United States, Belize, and a few Caribbean nations for weather, cooking, and body temperature.
Kelvin is the SI base unit for temperature and starts at absolute zero. It is used in physics and chemistry, where 0 K is the theoretical absence of all thermal energy.
The formula is exact, not an approximation. It was fixed by international agreement in 1948 and links the two scales at every point, including the -40 coincidence.
Common uses
- Reading a recipe from a U.S. site and converting its oven temperature to Celsius for a European oven.
- Checking a weather forecast in Fahrenheit while traveling and understanding it in Celsius.
Frequently asked questions
- Why is -40 the same in both scales?
- The scales cross at -40 because the offset and slope of the two formulas intersect there. It is a useful mnemonic and also the point where Celsius and Fahrenheit readings coincide.
- Is 0 °C the same as absolute zero?
- No. Absolute zero is -273.15 °C (0 K). 0 °C is the freezing point of water under standard atmospheric pressure.
- What is a normal body temperature?
- About 37 °C, which is 98.6 °F. A fever is generally considered to begin at 38 °C (100.4 °F).
- Why 9/5 and not 1.8?
- They are the same value. 9/5 is the exact fraction; 1.8 is the decimal approximation and introduces floating-point error in code.