Convert Fahrenheit to Celsius (°F to °C)

This direction is for when you already have a Fahrenheit reading — a US oven dial, a US weather forecast, a US thermostat, a fever reading from a US-style thermometer — and need it in Celsius, the scale used for everyday temperatures almost everywhere outside the United States.

Baking is the most common trigger: a US recipe calling for 350 °F converts to 176.7 °C, which is why so many non-US versions of American recipes simply round it to 180 °C. Because the scales are offset rather than proportional, halving or doubling a Fahrenheit oven temperature to guess the Celsius figure gives a badly wrong answer — always use the full formula.

US weather reports are the other everyday case: a forecast high of 75 °F is about 24 °C, and a cold snap at 20 °F is −6.7 °C, well below freezing even though the Fahrenheit number alone doesn't look obviously negative. Travelers checking a US forecast before a trip often misjudge how to dress because they read the Fahrenheit number the way they'd read a Celsius one.

Fever readings from a Fahrenheit thermometer need converting for anyone using metric medical guidance: the commonly cited normal baseline of 98.6 °F is 37 °C, and a reading of 101 °F — often flagged as a fever in US contexts — is 38.3 °C, which is useful to know when checking it against a metric fever threshold.

US cooking instructions lean on a handful of Fahrenheit thermometer targets that have no round metric twin. The internal temperatures usually quoted for doneness are 165 °F for poultry, which is 73.9 °C, and 145 °F for whole cuts, which is 62.8 °C. Barbecue recipes go the other way and describe smoking low and slow at 225 °F, or 107.2 °C, a setting near the bottom of most metric oven dials, while deep-frying instructions cluster between 350 °F and 375 °F, or 176.7 °C to 190.6 °C.