Convert celsius to fahrenheit

°F = °C × 9/5 + 32

Temperature is the one common conversion that is not a simple multiplication. The two scales have different zero points as well as different step sizes, so you scale first and then shift. Doing it in the wrong order — adding 32 before multiplying — is the classic mistake.

Double it and add 30. At 10 °C the shortcut is exact (50 °F); at 20 °C it gives 70 against the true 68; at 30 °C it gives 90 against 86. Good enough to decide on a jacket, not good enough for an oven or a thermometer.

And one fixed point worth remembering: −40 °C is −40 °F. It is the only temperature where the two scales agree.

• 180 °C = 356 °F — which American recipes round to 350 °F
• 200 °C = 392 °F — rounded to 400 °F
• 37 °C = 98.6 °F — the traditional normal body temperature
• 38 °C = 100.4 °F — the usual fever threshold
• 25 °C = 77 °F — a warm day

When the Swedish astronomer Anders Celsius published his scale in 1742, water boiled at 0 and froze at 100. The scale was reversed shortly after his death into the form used today. For two centuries it was called "centigrade"; the name Celsius was adopted internationally in 1948.

The Celsius scale is defined from the kelvin, the SI unit of temperature: the SI Brochure published by the International Bureau of Weights and Measures (BIPM) sets t/°C = T/K − 273.15, and since 2019 the kelvin rests on a fixed value of the Boltzmann constant. NIST Special Publication 811, the US guide to the SI gives the Fahrenheit relationship used on this page, a degree Fahrenheit being exactly 5/9 of a degree Celsius with the scales offset by 32 degrees.