Quick answer: Gas mark 4 is 180°C in a conventional electric oven and 160°C in a fan oven, which matches 350°F in American recipes. It is the classic “moderate” oven. The exact conversion of 350°F is 176.7°C, so recipe writers round it up to 180°C, and fan ovens are set about 20°C lower.
Gas mark 4 turns up in older British cookbooks, on the back of flour bags and in plenty of family recipe cards, but most UK kitchens now have an electric oven marked in degrees Celsius. This short explainer gives you the right dial setting for each type of oven. For spoons, cups, grams and every other kitchen conversion, see the UK cooking measurements guide.
What is gas mark 4 in a fan oven?
Gas mark 4 in a fan oven is 160°C. In a conventional (top and bottom heat) electric oven, use 180°C instead.
Many UK recipes now print all three figures together, for example “180°C/160°C fan/gas 4”. When a recipe gives only “180°C”, it usually means a conventional oven, so take 20°C off for fan. When it says “160°C fan”, it has already been adjusted and you should not reduce it again.
Why is a fan oven set 20°C lower?
A fan keeps hot air moving over the food, so it cooks faster at the same dial temperature. Still air forms an insulating layer around a cake tin or roasting tray. Moving air strips that layer away and transfers heat more quickly, which is why a fan oven at 160°C behaves much like a conventional oven at 180°C.
The 20°C rule is a guide rather than a law of physics. Consumer group Which? and oven makers such as Smeg both publish fan settings roughly 20°C below the conventional figure, but some newer ovens with very efficient fans suggest a smaller drop. Your oven’s manual is the final word, especially for combination or multifunction settings.
How does gas mark 4 compare with gas marks 3 and 5?
Each gas mark in this range is roughly 10°C to 15°C apart. Gas mark 3 is a little gentler, and gas mark 5 is the step up to a moderately hot oven. The table shows the usual UK settings alongside the American Fahrenheit figure.
| Gas mark | Conventional oven | Fan oven | Fahrenheit | Description |
|---|---|---|---|---|
| 3 | 170°C | 150°C | 325°F | Moderately slow |
| 4 | 180°C | 160°C | 350°F | Moderate |
| 5 | 190°C | 170°C | 375°F | Moderately hot |
You may see gas mark 3 printed as 160°C in some charts. That is because 325°F works out at 162.8°C, which sits between the two round numbers. Gas mark 4 is less ambiguous: 350°F is 176.7°C, and every mainstream chart rounds it to 180°C.
What is usually cooked at gas mark 4?
Gas mark 4 is the default for most cakes and many bakes. It is hot enough to set a sponge and brown the top, but gentle enough that the middle cooks through before the edges dry out. Typical examples include:
- Victoria sponges, loaf cakes and cupcakes
- Many biscuits, flapjacks and traybakes
- Fruit crumbles and baked puddings
- Reheating covered dishes such as lasagne or a pie made earlier
Follow your own recipe’s timings, and make sure meat and reheated food are piping hot throughout.
Is 180°C exactly the same as gas mark 4?
Not exactly, but the difference is too small to matter in practice. Gas marks were defined in Fahrenheit: from gas mark 1 upwards, each mark adds 25°F to a starting point of 250°F, so gas mark 4 is 250 + (4 × 25) = 350°F. Converting with the formula °C = (°F − 32) × 5 ÷ 9 gives 176.7°C. Oven thermostats rarely hold a temperature closer than a few degrees, so 180°C is the sensible dial setting.
If you are converting other numbers from an American recipe, the Fahrenheit to Celsius converter gives exact figures, and the general cooking converter handles cups, ounces and spoons.
Frequently asked questions
What is gas mark 4 in Celsius for a fan oven?
Gas mark 4 is 160°C in a fan oven. In a conventional electric oven without the fan, set the dial to 180°C.
What is gas mark 4 in Fahrenheit?
Gas mark 4 is 350°F. This is the most common baking temperature in American recipes, and it converts to 176.7°C, which UK recipes round to 180°C.
Is 170°C fan the same as gas mark 4?
No. 170°C fan is equivalent to about 190°C conventional, which is gas mark 5. For gas mark 4 in a fan oven, use 160°C.
Should I reduce the temperature if a recipe already says fan?
No. A figure labelled fan has already been reduced. Only take off about 20°C when the recipe gives a conventional temperature or a gas mark and you are using the fan setting.
Does a fan oven cook faster at gas mark 4 equivalent?
At 160°C fan, cooking times are usually close to the recipe time for 180°C conventional. Start checking a few minutes early, because ovens and fans vary.
Sources
- Which?: oven temperature conversion (Celsius, Fahrenheit, gas mark and fan)
- Smeg UK: oven temperature conversions
- National Physical Laboratory (NPL), the UK’s national measurement institute, for temperature scale definitions