Fan Oven / Conventional Oven Temperature Converter
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
To go from a recipe written for a conventional oven to a fan oven setting, reduce the temperature by 20°C (about 35-40°F). A recipe calling for 180°C (350°F) conventional should therefore be set to about 160°C (320°F) with the fan on.
Explanation
A conventional oven heats using two heating elements, top and bottom, without circulating the air: heat diffuses more slowly and less evenly inside the oven cavity. A fan (convection) oven adds a fan that continuously circulates hot air, which spreads heat much more evenly and speeds up heat transfer to the food. This increased efficiency allows cooking at a lower temperature for an equivalent result: the commonly used rule is to reduce the temperature by 20°C compared to a recipe designed for a traditional conventional oven. Without this adjustment, a dish cooked with the fan on at the temperature intended for a conventional oven risks browning too quickly on the surface, or even drying out, before the inside has had time to cook through. This calculator works both ways: reduce by 20°C to go from conventional to fan, or add 20°C for the reverse operation (adapting a recipe designed for a fan oven to a conventional-only oven). This 20°C rule remains a general guideline rather than a universal exact value: some oven manufacturers sometimes recommend a slightly different adjustment depending on their specific model, the oven's manual remaining the most reliable reference when in doubt. To convert this same temperature between Celsius, Fahrenheit, and gas mark, see our oven temperature conversion calculator.
Example: a recipe at 180°C in a conventional oven
Inputs
Given temperature: 180°C. Direction: to fan oven.
Calculation
Adjusted temperature = 180 − 20 = 160°C.
Result
Set your fan oven to 160°C for a result equivalent to 180°C in a conventional oven.
Frequently asked questions
Should I also adjust the cooking time, not just the temperature?
Yes, a fan oven generally cooks a bit faster thanks to better air circulation: in addition to lowering the temperature, it's common to shorten the cooking time slightly (by a few minutes on a 30- to 40-minute bake), checking on the dish toward the end rather than blindly following the time given for a conventional oven.
Does this 20°C rule apply to all ovens?
It's a widely used and commonly recommended general guideline, but some manufacturers sometimes indicate a slightly different adjustment depending on the exact power and design of their oven model. When in doubt, the oven's manual or the manufacturer's instructions remain the most reliable reference for your specific appliance.
Are some dishes not recommended with a fan oven?
Some delicate baked goods (soufflés, certain cakes that need to rise undisturbed) are sometimes preferred with conventional heat, since the air circulation from the fan can slightly affect their texture or rise. For most savory dishes and many common baked goods, a fan oven works well and often allows more even cooking across several oven racks at once.