The rule: drop 20°C (about 25°F)
To convert a conventional temperature to a fan oven, reduce it by 20°C — or about 25°F.
So a recipe that says 180°C conventional becomes 160°C fan; 350°F becomes about 325°F. Alternatively, keep the temperature the same and cut the baking time by roughly 25% — but for most baking, lowering the temperature gives more even, predictable results.
Don’t do both at once. Reducing the temperature AND the time will leave you underbaked. Pick one — usually the temperature.
Fan oven conversion chart
| Conventional | Fan | Conventional (°F) | Fan (°F) |
|---|---|---|---|
| 160°C | 140°C | 325°F | 300°F |
| 180°C | 160°C | 350°F | 325°F |
| 190°C | 170°C | 375°F | 350°F |
| 200°C | 180°C | 400°F | 375°F |
| 220°C | 200°C | 425°F | 400°F |
| 230°C | 210°C | 450°F | 425°F |
When not to use the fan
Fan is great for roasting, biscuits, and baking several trays at once. But the moving air can dry out or skin delicate bakes, so many bakers switch to conventional (or just the bottom element) for:
- Delicate sponges, soufflés, and some cheesecakes that can crack or dry on top.
- Tall, slow-baking cakes where you want a gentle, even rise.
- Custards and meringues that prefer still, gentle heat.
If your bakes are browning or burning at the temperature the recipe states, the most likely reason is a fan oven that wasn’t turned down. Drop 20°C and check early.