Oven Temperature Converter

Oven temperatures come in three incompatible systems and one modifier. Celsius and Fahrenheit are a straightforward calculation. Gas marks are not: they are discrete settings that map onto roughly 14 °C steps at the top of the range but bunch together at the bottom, where mark ¼ and mark ½ are only 10 °C apart.

The modifier is the one that ruins food. A fan or convection oven circulates hot air, so it transfers heat faster and cooks noticeably quicker at the same dial setting. Recipes are almost always written for a conventional oven, so a fan oven needs about 20 °C knocked off. Skipping that is the single most common reason a cake comes out dark on the outside and raw in the middle.

One caveat no converter can fix: domestic ovens are frequently 10–20 °C out from their own dial, and the variation across a single oven cavity can be larger still. An oven thermometer costs very little and settles the question permanently.