Oven Temperature Gas Mark Converter
Convert oven temperatures between Celsius, Fahrenheit and UK gas marks, with the fan-oven equivalent worked out too.
How it works
°F = °C × 9/5 + 32 · Gas mark = (°F − 250) ÷ 25 · Fan oven ≈ conventional °C − 20
Celsius and Fahrenheit convert by the standard linear formula, and UK gas marks follow an even 25 °F step above a 275 °F baseline for mark 1 — so each mark is 25 °F apart. Fan (convection) ovens circulate air and heat food faster, so the usual guidance is to set them about 20 °C below the temperature a conventional recipe states.
Worked example
A recipe says 180 °C. In Fahrenheit that is 180 × 9/5 + 32 = 356 °F, which is (356 − 250) ÷ 25 = 4.2, rounding to gas mark 4. In a fan oven, set roughly 180 − 20 = 160 °C.
Frequently asked questions
How do gas marks relate to Fahrenheit?
Each gas mark is 25 °F apart: gas mark 1 is 275 °F, gas mark 4 is 350 °F, gas mark 6 is 400 °F. The formula (°F − 250) ÷ 25 gives the mark directly.
Why lower the temperature for a fan oven?
A fan circulates hot air, heating the surface of food faster and more evenly than a static oven. Dropping about 20 °C compensates so timings from a conventional recipe still work.
Is 350 °F really the most common baking temperature?
Yes — 350 °F (180 °C, gas mark 4) is the default for many cakes, cookies and casseroles because it browns and sets without scorching the outside before the centre cooks.
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This calculator is for educational purposes. Double-check important results before acting on them.