Oven temperature chart: Celsius, Fahrenheit and gas mark
A clear guide to matching gas marks with Celsius and Fahrenheit, why the numbers round, and how to adapt between British and American recipes.
The three ways ovens are labelled
Where you live decides how your oven is marked. Most of the world uses Celsius, the United States uses Fahrenheit, and older British ovens and recipes use gas marks numbered 1 to 9. A recipe written in one system can feel opaque in another, which is why a moderate oven might read 180 C, 350 F or gas 4 depending on the cookbook. All three describe the same heat, so converting between them is about translation, not different cooking.
How gas marks line up with degrees
The common British chart pins gas 1 at about 140 C and climbs in steady steps: gas 3 is 170 C, gas 4 is 180 C, gas 5 is 190 C, gas 6 is 200 C, gas 7 is 220 C, and gas 9 reaches 240 C. Because these are fixed points rather than a smooth formula, converting a random Celsius value returns the nearest mark rather than an exact one. That is fine in practice, since oven thermostats and home ovens both drift by more than the gap between two marks.
Why the Fahrenheit numbers get rounded
Convert 180 C precisely and you get 356 F, yet recipes say 350 F. The exact formula multiplies Celsius by 9/5 and adds 32, but bakers round to the nearest tidy 25 degrees because ovens are not accurate enough to care about a few degrees either way. This converter shows the exact converted figure so you can see the real value, and you can safely round it to the nearest 25 when you set the dial. The reverse is true going from Fahrenheit to Celsius.
Adapting British and American recipes
When you cook an American recipe on a Celsius oven, convert the Fahrenheit target down and round to a sensible mark: 350 F becomes about 180 C, and 425 F becomes about 220 C. Going the other way, a British gas 6 recipe on a US oven is around 400 F. If the recipe was written for a conventional oven and yours is a fan or convection model, lower the result by roughly 20 C or 25 F, since moving air cooks faster at the same reading.