Oven Temperature Converter

How the conversion works

Two formulas cover Fahrenheit and Celsius:

Celsius = (Fahrenheit - 32) x 5 / 9

Fahrenheit = Celsius x 9 / 5 + 32

For 350 °F: 350 - 32 = 318, and 318 x 5 / 9 = 176.7 °C. For 200 °C: 200 x 9 / 5 = 360, and 360 + 32 = 392 °F.

Neither answer is a number you can set on an oven, which is where the second step comes in.

Why the answer is rounded

Oven dials and recipe writers work in steps. Fahrenheit recipes move in jumps of 25 degrees: 325, 350, 375, 400. Celsius recipes use 10 or 20 degree jumps: 160, 180, 200, 220. A cookbook translated from one system to the other does not print 177 °C. It prints 180 °C, the nearest setting a Celsius oven has.

The converter shows that standard setting as the main result, because it is what you will turn the dial to. Open “Show the math” to see the exact figure it was rounded from. Across the standard settings, the rounding is never more than about 7 °C.

Gas marks

Gas marks are the numbers on the dial of a British gas oven. Above mark 1 the pattern is simple: each mark is 25 °F hotter than the one before.

• Gas mark 1 is 275 °F (140 °C)
• Gas mark 4 is 350 °F (180 °C)
• Gas mark 6 is 400 °F (200 °C)
• Gas mark 9 is 475 °F (240 °C)

So a quick way to convert is: multiply the gas mark by 25 and add 250. Gas mark 5 is 5 x 25 + 250 = 375 °F. Below mark 1 the dial has two half steps, 1/4 at 225 °F and 1/2 at 250 °F, used for meringues and slow cooking. Type them into the converter as 1/4 or 1/2.

The settings you will use most

Most baking and roasting happens at a handful of temperatures. These are the standard pairs:

• 300 °F is 150 °C, gas mark 2
• 325 °F is 170 °C, gas mark 3
• 350 °F is 180 °C, gas mark 4
• 375 °F is 190 °C, gas mark 5
• 400 °F is 200 °C, gas mark 6
• 425 °F is 220 °C, gas mark 7
• 450 °F is 230 °C, gas mark 8

You may see 325 °F listed as 160 °C on some charts. The exact conversion is 163 °C, which sits between the two, so either setting is within a few degrees.

Worked example

A British recipe says: “Bake at 190 °C, 170 °C fan, gas 5.” You have an American oven.

1. 190 x 9 / 5 + 32 = 374 °F.
2. The nearest standard setting is 375 °F, which matches gas mark 5 on the chart.
3. Set the oven to 375 °F.

Going the other way, an American recipe asks for 425 °F. (425 - 32) x 5 / 9 = 218.3 °C, and the standard setting is 220 °C, gas mark 7. In a fan oven you would set 200 °C.

Fan ovens

A fan oven, called a convection oven in the United States, blows hot air around the food. Heat reaches the surface faster, so the same dial setting cooks harder than it would in an oven without a fan.

The usual recipe convention is to set a fan oven about 20 °C, or 25 °F, lower than the temperature given for a conventional oven. The converter and the chart both show that fan setting next to every result. Many British recipes already print both, as in “180 °C, 160 °C fan”.

Tips and common mistakes

Check which oven the recipe was written for. An American recipe that says 350 °F almost always means a conventional oven. If you run that in a fan oven at the straight conversion of 180 °C, the outside will brown before the middle is done.

Do not convert twice. If a recipe already lists a fan temperature, use it as printed instead of subtracting another 20 degrees.

An oven thermometer is worth having. The number on the dial is what the oven is aiming for, and a thermometer hung from the middle shelf tells you what it reached. If yours reads 15 degrees low at every setting, you can correct for it every time you bake.