Convert Celsius to Fahrenheit

The formula

°F = °C × 9/5 + 32

Celsius to Fahrenheit — quick reference

The two scales do not share a zero, so there is no per-degree multiplier

A rise of ten Celsius degrees is a rise of eighteen Fahrenheit degrees, but ten degrees Celsius is not eighteen degrees Fahrenheit. The offset has to be applied after the scaling, and skipping it is the commonest mistake made in the head. The scales cross at minus forty, where both read the same number, and that is the one anchor worth committing to memory.

The other anchor is body temperature. Normal body temperature of 37 °C converts to 98.6 °F, and the decimal is an accident of translation: the nineteenth-century measurement behind it was taken in whole Celsius degrees and was never that precise. A British doctor saying 38 °C is quoting a fever threshold, which American guidance states as 100.4 °F — the same number, converted.

Oven temperatures are conventions, and 180 is not 350

European recipes default to 180 °C and American ones to 350 °F. Converted exactly, 180 °C is 356 °F and 350 °F is 176.7 °C. The recipes mean each other regardless: both are the standard moderate oven in their own tradition, and no domestic oven holds a temperature to six degrees anyway. The pairing continues upward, 200 °C with 400 °F and 220 °C with 425 °F.

The correction that does matter is the fan. A British recipe stating 180 °C means a conventional oven unless it says fan, and a fan or convection oven wants about 20 °C less for the same result — 160 °C, near enough 325 °F. Gas marks follow the conventional ladder rather than the fan one: gas mark 4 is 180 °C and 350 °F.

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