Oven Temperature Conversion: °F, °C, Gas Mark & Fan

The Fahrenheit–Celsius formula

The conversion is exact: °C = (°F − 32) × 5/9, and °F = °C × 9/5 + 32. For example, 350°F − 32 = 318, times 5/9 = 176.7 °C, which cooks round to 180 °C. The two scales cross at −40°, where −40°F equals −40 °C — a handy fact but far below any oven setting.

In practice you rarely need the raw formula, because oven dials move in fixed steps. Cooks memorize a short ladder of landmarks — 325, 350, 375, 400, 425°F — and their Celsius partners, then round to the nearest 10 °C. A converter is quickest for the in-between values a recipe occasionally throws at you.

Gas mark: the third scale

British and older ovens use gas marks, a numbered scale where each step is about 25°F (14 °C). The key landmarks: gas 3 = 325°F (160 °C), gas 4 = 350°F (180 °C), gas 5 = 375°F (190 °C), gas 6 = 400°F (200 °C), and gas 7 = 425°F (220 °C). Gas 1 is a low 275°F (140 °C) and gas 9 a fierce 475°F (240 °C).

Notice that gas 4 lines up with the everyday baking temperature of 350°F / 180 °C — the setting most cakes, cookies and roasts default to. If a British recipe only gives you a gas mark, match it to this ladder and you will land within a few degrees of the intended heat.

Fan (convection) ovens: subtract 20 °C

A fan (convection) oven circulates hot air, so food cooks faster and more evenly than in a conventional oven at the same dial setting. The standard adjustment is to lower the temperature by about 20 °C (or roughly 25–50°F): a recipe written for 350°F conventional becomes about 160 °C on a fan setting.

Watch the timing too: because fan ovens are more efficient, foods can also finish 5 to 10 minutes early, especially small items like cookies. When in doubt, drop the temperature by 20 °C, check a few minutes before the stated time, and trust visual cues — golden edges and a clean skewer — over the clock.

Frequently asked questions

What is 350°F in Celsius?

About 180 °C. The exact math gives 176.7 °C, which cooks round to 180 °C — the standard baking temperature, equal to gas mark 4.

How do I adjust a recipe for a fan oven?

Lower the stated temperature by about 20 °C and start checking 5 to 10 minutes early. Fan ovens circulate heat, so they cook faster and more evenly than conventional ones.

What temperature is gas mark 6?

Gas mark 6 is 400°F, or 200 °C — a fairly hot setting used for roasting vegetables, pastry and many breads.

Should I preheat the oven before converting?

Conversion and preheating are separate steps. Convert the target temperature first, set the dial, then let the oven fully preheat — usually 10 to 15 minutes — before the food goes in, so it cooks at the intended heat from the start.