UK Oven Temperature & Cooking Conversion Cheat Sheet: Celsius, Gas Mark, Fan Oven & Time Adjustments

Overview

Recipes do not always use the same oven language. A British cookbook may give a Gas Mark, an American recipe may use Fahrenheit, and a modern appliance may display only fan-assisted Celsius. The conversion is usually straightforward, but temperature is only one part of the result. The size and material of the tin, the amount of food, whether ingredients are chilled or frozen, and the way your particular oven runs can all change the cooking time.

Start with the table below, then use the scenario checklist rather than treating a conversion as an exact guarantee. For cakes, bread, pastry and other bakes, the structure of the food matters as much as the oven setting. For meat, fish and reheated dishes, check the centre is properly cooked before serving.

These are useful rounded equivalents, not a substitute for your appliance manual or the recipe writer's instructions. If a recipe says Gas Mark 6, begin with 200°C in a conventional oven, around 180°C in a fan oven, or 400°F. Always check whether the stated temperature is for a fan or non-fan oven before converting.

Checklist by scenario

Converting a conventional oven recipe to a fan oven

• Reduce the temperature by about 20°C as a starting point. For example, 200°C conventional becomes approximately 180°C fan.
• Keep the recipe's stated cooking time initially, but begin checking slightly earlier, particularly for biscuits, pastry, shallow tray bakes and small portions.
• Leave space around tins and trays so hot air can circulate. Crowding can cancel out some of the fan oven's advantage.
• Rotate or move food only if your oven has a clear hot spot; opening the door repeatedly can slow baking and cooking.

Fan ovens often brown food efficiently, so a lower temperature can help prevent a dark top or dry edges. For delicate cakes, follow the recipe's stated fan setting where one is provided rather than applying a second conversion.

Converting between Celsius, Fahrenheit and Gas Mark

• Identify the oven type first: the table's main Celsius column is for conventional ovens.
• For Gas Mark 6, use 200°C conventional, 180°C fan or 400°F.
• Use the nearest practical setting on your appliance instead of chasing a fraction of a degree.
• Record successful adjustments beside recipes you make regularly.

For more ingredient and oven reference work, see our guide to cooking substitutions and conversions in the UK.

Using an air fryer or air-fryer oven

• Begin about 20°C below the recipe's conventional oven temperature. A recipe at 200°C conventional may start at 180°C in an air fryer.
• Expect food to cook more quickly because the cooking chamber is smaller and the air movement is strong.
• As a practical first estimate, check food around 20–25% earlier than the stated oven time.
• Cook in a single layer where possible and avoid blocking the basket or vents.
• Check small items early: chips, vegetables, breaded foods and individual pastries can change from lightly browned to overdone quickly.

Air-fryer models vary considerably. Treat temperature and time as a starting point, and use the appliance's manual for its recommended settings. A full-size air-fryer oven may behave differently from a compact basket model.

Changing the quantity or pan size

Do not automatically double the cooking time when you double a recipe. A larger quantity in a wider, shallower dish may cook in a similar time, while the same quantity in a deeper dish usually needs longer. Use this workflow:

1. Scale the ingredients accurately, including raising agents, liquid and seasoning.
2. Choose a tin or dish that keeps the mixture at roughly the original depth.
3. Keep the oven temperature the same unless you are also changing oven type.
4. Start checking at the original recipe time, then extend in short intervals.
5. Use visual and physical cues: a cake should be set in the centre, pastry should look properly coloured, and a savoury bake should be piping hot throughout.

For tray bakes, the surface area affects speed more than the recipe's total number of portions. A larger shallow tray may reduce the time; a smaller, deeper tin may increase it. When in doubt, compare the new tin's dimensions and batter depth rather than relying on a fixed multiplier.

What to double-check

• Preheating: Allow the oven to reach temperature before adding most bakes. A cold start changes both timing and texture.
• Oven accuracy: The displayed temperature may not match the temperature at the shelf. If results are consistently pale, burnt or uneven, an inexpensive oven thermometer can help identify a pattern.
• Shelf position: The middle shelf is a sensible default for cakes and general baking. Follow recipe-specific guidance for roasting, grilling or crisping.
• Ingredient temperature: Frozen food generally needs more time than chilled or fresh food. Do not use a browned surface alone to judge a frozen centre.
• Food safety: For meat, poultry, fish and reheated leftovers, check the thickest part is fully cooked and steaming hot where appropriate. Follow the recipe and packaging instructions for the food you are using.
• Dish material: Dark metal tins can brown more quickly than pale ceramic or glass dishes. Glass and ceramic dishes may also need care when moved between very different temperatures.

Cooking time is best treated as a range. The listed time tells you when to begin checking; it is not always the moment the food will be ready.

Common mistakes

• Reducing the temperature twice: If a recipe already specifies a fan oven, do not reduce it again. Check the wording before converting.
• Using the Fahrenheit number as Celsius: 400°F is approximately 200°C, not 400°C.
• Changing temperature and time without a plan: Make one main adjustment at a time so you can understand the result.
• Overfilling a tin: A deeper mixture can remain unset in the centre while the outside browns. Use a suitable tin or divide the mixture between two.
• Opening the door too early: Cakes and soufflé-style bakes can lose heat and structure. Check through the glass where possible.
• Assuming every air fryer works alike: Basket size, fan strength and heating element position all affect browning and timing.
• Ignoring carry-over cooking: Some foods continue cooking briefly after removal. Rest roast meats and allow bakes to set as directed before cutting.

If you are planning several make-ahead dishes, our UK meal prep and batch cooking guide can help you organise oven space, cooling and storage. For beginner-friendly baking examples, see easy British baking recipes for beginners.

When to revisit

Return to this checklist whenever a recipe uses an unfamiliar temperature scale, you buy a new oven or air fryer, or you change the tin, dish or batch size. It is also worth reviewing your notes after cooking a recipe for the first time: record the appliance setting, shelf, dish material and actual time. That small record becomes more useful than a generic conversion when you repeat the dish.

Recheck timings when moving between seasons if ingredients are being used from frozen rather than fresh, or when your usual appliance is replaced. Before cooking, follow this final routine: identify the oven type, convert the temperature, assess the food depth, preheat fully, set an early timer, and check the centre before serving. That approach keeps oven temperature conversion practical while leaving room for the differences between recipes, tins and real kitchens.