Fan Oven Conversion: Convection Temperature and Time Chart
For a fan (convection) oven, lower the recipe temperature by 20 °C, or 25 °F. So 180 °C conventional becomes 160 °C fan, and 350 °F becomes 325 °F convection. Start checking for doneness a few minutes early.
Why fan ovens cook faster
A still oven heats food mainly through hot air that sits around it, plus radiant heat from the walls. That air forms a thin, cooler "boundary layer" around the food that acts like insulation. A convection oven has a fan that keeps blowing that layer away, so fresh hot air keeps touching the surface.
The result: heat moves into food faster, and the surface dries and browns more quickly. Lowering the temperature compensates so the outside doesn't finish before the inside.
Conventional to fan: Celsius
| Recipe (conventional) | Fan oven | Gas mark |
|---|---|---|
| 140 °C | 120 °C | 1 |
| 150 °C | 130 °C | 2 |
| 160 °C | 140 °C | 3 |
| 170 °C | 150 °C | 3 |
| 180 °C | 160 °C | 4 |
| 190 °C | 170 °C | 5 |
| 200 °C | 180 °C | 6 |
| 210 °C | 190 °C | 6–7 |
| 220 °C | 200 °C | 7 |
| 230 °C | 210 °C | 8 |
| 240 °C | 220 °C | 9 |
Conventional to convection: Fahrenheit
| Recipe (conventional) | Convection | Fan °C equivalent |
|---|---|---|
| 300 °F | 275 °F | 130 °C |
| 325 °F | 300 °F | 140–150 °C |
| 350 °F | 325 °F | 160 °C |
| 375 °F | 350 °F | 170 °C |
| 400 °F | 375 °F | 180 °C |
| 425 °F | 400 °F | 200 °C |
| 450 °F | 425 °F | 210 °C |
| 475 °F | 450 °F | 220 °C |
Recipe already says "fan"?
UK and Australian recipes often give both numbers, like "200 °C / 180 °C fan / gas 6". Use the fan figure as written. If a recipe gives only one number and doesn't say which, assume conventional unless it's a recent UK recipe, where it's worth checking the intro or method notes.
Time adjustments
| Food | Temperature | Time |
|---|---|---|
| Cakes, cookies, muffins | Drop 20 °C / 25 °F | About the same; check 5 minutes early |
| Bread | Drop 20 °C / 25 °F | About the same |
| Roast meat and poultry | Keep the same or drop slightly | 10–25% shorter |
| Roast vegetables | Keep the same | 10–20% shorter, more browning |
| Frozen convenience foods | Follow the package fan setting | As package |
| Large batches on several racks | Drop 20 °C / 25 °F | About the same, more even |
Always judge by doneness, not the clock. For meat, use a thermometer and allow for carryover cooking of a few degrees as it rests.
When to switch the fan off
- Custards, cheesecakes and crème brûlée: moving air can skin or crack the surface.
- Soufflés and chiffon or angel food cakes: strong airflow can make them rise lopsided.
- Light, loose things: parchment, puff pastry edges and coconut toppings can lift or scorch.
- Meringues are an exception: a gentle fan helps them dry.
Air fryers and fan-only settings
An air fryer is a small, very strong convection oven. Start about 15–20 °C (25 °F) below a conventional-oven recipe and cut the time by roughly 20%, shaking or flipping halfway through. Many ovens also have "true convection" (an extra heating element around the fan) versus plain "fan assisted". True convection is more even, and the 20 °C rule still works for both.
For the full Fahrenheit-to-Celsius chart, see oven temperature conversion.
Questions
Is 180 °C fan the same as 200 °C conventional?
Roughly, yes. A fan oven set to 180 °C cooks about like a conventional oven at 200 °C, because moving air transfers heat faster.
Do I reduce the temperature or the time in a convection oven?
Usually the temperature: drop it by 20 °C or 25 °F and start checking a little early. For roasts you can keep the temperature and cut the time by 10 to 25 percent instead.
Does my oven already adjust for convection?
Many newer North American ovens have an automatic convection conversion that subtracts 25 °F for you when you choose convection bake. Check the manual; if yours does, enter the recipe temperature unchanged.
Should I use the fan for cakes?
You can, at the lower temperature, but very delicate bakes such as soufflés, chiffon cakes and custards often do better without the fan because moving air can dry or crack the surface.