How to Convert Oven Temperatures

Three ways of describing the same heat

Oven temperature is written in different ways around the world. Recipes from the United States use degrees Fahrenheit (°F). Most of the rest of the world uses degrees Celsius (°C). Recipes from the UK and some older cookbooks may use gas marks, a numbered scale found on gas ovens.

All three describe the same thing, how hot the oven is, so any recipe can be converted. Celsius and Fahrenheit follow exact formulas, while gas marks are a set of steps that you read from a chart.

The key is to pick a target the oven can actually be set to. Many ovens can only be set in steps of 5 or 10 degrees, and gas ovens only have the numbered marks, so an exact decimal result is never needed.

Celsius to Fahrenheit

Multiply by 9, divide by 5, then add 32:

°F = °C × 9 ÷ 5 + 32

For 180 °C, the sum is 180 × 9 ÷ 5 = 324, then 324 + 32 = 356 °F. For 200 °C, you get 360 + 32 = 392 °F. For 160 °C, it is 288 + 32 = 320 °F.

Recipes rarely use the exact result. A cook who sees 356 °F will set the oven to 350 °F, and one who sees 392 °F will pick 400 °F. Round to the nearest value your oven dial can show.

A quick mental shortcut is to double the Celsius value and add 30 for a rough Fahrenheit figure. For 180 °C that gives 390 °F, which is higher than the true 356 °F, so use it only for a first estimate at low temperatures, not for baking.

Fahrenheit to Celsius

Subtract 32, multiply by 5, then divide by 9:

°C = (°F − 32) × 5 ÷ 9

For 350 °F, subtract 32 to get 318, multiply by 5 to get 1,590, and divide by 9 to get about 176.7 °C. For 425 °F: 393 × 5 ÷ 9 is about 218.3 °C. For 400 °F: 368 × 5 ÷ 9 is about 204.4 °C.

Again, round to a practical setting. In Celsius, recipes usually step in tens, so 176.7 °C is written as 175 or 180 °C, and 218.3 °C is written as 220 °C.

A shortcut in the other direction is to subtract 30 and halve the Fahrenheit value. For 350 °F that gives 160 °C, which is about 17 °C low, so again treat it as a guess and prefer the formula.

Gas mark chart

Gas marks do not follow a formula, so the usual approach is a chart. This list shows the common values, in °C and °F:

• Gas mark ¼: 110 °C, 225 °F
• Gas mark ½: 120 °C, 250 °F
• Gas mark 1: 140 °C, 275 °F
• Gas mark 2: 150 °C, 300 °F
• Gas mark 3: 170 °C, 325 °F
• Gas mark 4: 180 °C, 350 °F
• Gas mark 5: 190 °C, 375 °F
• Gas mark 6: 200 °C, 400 °F
• Gas mark 7: 220 °C, 425 °F
• Gas mark 8: 230 °C, 450 °F
• Gas mark 9: 240 °C, 475 °F

These values are rounded, and charts can differ by a few degrees. If a temperature falls between two marks, choose the nearest one.

As a pattern, each step between marks 1 and 9 adds either 10 °C or 20 °C. The scale is not perfectly even, which is why a chart is better than a formula.

Why the numbers do not match exactly

You will notice that 350 °F is paired with 180 °C even though the formula gives 176.7 °C, and that 400 °F is paired with 200 °C even though the formula gives 204.4 °C. Recipe writers round to useful numbers, and ovens are not accurate to a single degree anyway.

A difference of 5 °C, or about 10 °F, rarely matters in a casserole or roast. It matters more in delicate bakes, such as macarons, meringues and custards, so for those use an oven thermometer and follow the recipe’s visual cues, such as color and doneness.

Real ovens can also differ from their dial setting by 10 °C or more. A cheap oven thermometer placed on the middle shelf shows what your oven really does, and you can then adjust the setting after converting.

Fan ovens and other adjustments

The conversions above assume the same type of oven. A fan (convection) oven circulates hot air and often cooks faster than a conventional one. Many recipes give separate temperatures for conventional and fan ovens, and a commonly quoted rule of thumb is to lower a conventional temperature by about 20 °C (about 25 °F) for a fan oven. This is an adjustment you make by hand after converting, and it varies by oven, so check your oven’s manual.

Also check the recipe itself: if it already states a fan temperature, do not reduce it again.

For example, a recipe that gives 200 °C conventional may say 180 °C fan. Converting 200 °C to Fahrenheit gives 392 °F, usually set at 400 °F, and the fan equivalent of that would be around 375 °F.

Using a converter

A cooking converter such as this one accepts a value in °C, °F or gas mark and shows the others, with temperatures rounded to whole degrees and a Celsius or Fahrenheit value shown as the nearest gas mark. It does not apply a fan-oven adjustment, so make that change yourself. Once you have the number, preheat fully before baking, because an oven that is still heating up will give uneven results.