Oven Temperature Converter

In short Gas mark 4 is 180 °C conventional, 160 °C in a fan oven and 350 °F, and the three scales do not line up neatly because gas marks were defined as their own series rather than derived from Celsius. The fan adjustment is the part that ruins baking. A fan oven moves hot air across the food, which transfers heat considerably faster than still air, so a fan oven set to the temperature a recipe states will cook hotter than the recipe intends — the standard correction is about 20 °C lower, and some manufacturers suggest cutting the time slightly as well. Recipes written for one and cooked in the other are the single most common reason for cakes that are dark outside and raw in the middle. The other reason is that your oven is probably not at the temperature it claims. A typical domestic oven is 20 to 30 °C out somewhere in its range without calibration, and many are worse at the extremes than in the middle. An oven thermometer costs very little and settles the question permanently, and once you know your oven runs 20 °C hot, every recipe you have ever struggled with makes sense at once.