fahrenheit to celsius converter

How to convert fahrenheit to celsius

Subtract 32, then multiply by 5/9. That undoes the offset before it scales the degree. 32 °F is 0 °C, 212 °F is 100 °C, and 98.6 °F is 37 °C. Doing the multiply first is the usual bug, and it makes a winter day look like a fever. The size of the degree is 5/9 of a Celsius degree, so a ten-degree Fahrenheit swing is only about 5.556 Celsius degrees.

A US forecast, a thermostat, or a recipe in °F that has to be cooked on a °C oven. 350 °F is 176.667 °C, which ovens often mark as 180. 72 °F is 22.222 °C, a normal indoor set point. If you are converting a delta ('the oil rose 20 °F'), skip the 32 and only multiply by 5/9.

Exact formula

Formula°C = (°F − 32) × 5/9

°C = (°F − 32) × 5/9 One °F is -17.2222222222 °C. Ten °F is -12.2222222222 °C. The worked example below uses that same conversion.

Conversion table

The fahrenheit column runs from -40 °F (-40 °C) through 400 °F (204.44 °C).

Worked example: Fahrenheit to Celsius

A US recipe at 350 °F is 176.67 °C after you subtract 32 and then multiply by 5/9. Ovens marked in Celsius often print 180 for that setting. The classic 98.6 °F fever line is 37 °C, which is 37 °C exactly for that textbook value and not a promise about a real patient. Water freezes at 32 °F, which is 0 °C. Doing the multiply before the subtraction makes a winter day look like a fever. A change of 18 °F is 10 °C and does not subtract 32.

Pitfalls for fahrenheit to celsius

• Subtract 32 before multiplying. (F − 32) × 5/9 is not the same as F × 5/9 − 32.
• 98.6 is 37 exactly only because 98.6 was chosen as 37 × 9/5 + 32. Real body temperature varies.
• Wind chill and heat index are already in the scale they were published in. Do not convert them twice.
• A Fahrenheit degree is smaller. Do not treat '10 degrees' as the same interval on both scales.