Quick answer: To convert a conventional oven temperature for a fan oven, subtract about 20°C. So 180°C becomes 160°C fan, 200°C becomes 180°C fan and 220°C becomes 200°C fan. Going the other way, add 20°C. Recipes that already say “fan” have been adjusted, so use those figures as written.
Most UK homes now cook with an electric fan oven, yet recipes still arrive in conventional Celsius, gas marks or American Fahrenheit. The chart below lines all four up so you can set the dial without guesswork. It is part of the site’s guide to UK cooking measurements, which also covers cups, spoons and weights.
Fan oven temperature conversion chart
Find your recipe’s figure in any column and read across for the fan setting. The Fahrenheit numbers are the round values American recipes use, and the gas marks follow the traditional British scale.
| Gas mark | Conventional °C | Fan °C | Fahrenheit | Oven description |
|---|---|---|---|---|
| ¼ | 110°C | 90°C | 225°F | Very cool |
| ½ | 120°C | 100°C | 250°F | Very cool |
| 1 | 140°C | 120°C | 275°F | Cool |
| 2 | 150°C | 130°C | 300°F | Slow |
| 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 |
| 6 | 200°C | 180°C | 400°F | Hot |
| 7 | 220°C | 200°C | 425°F | Hot |
| 8 | 230°C | 210°C | 450°F | Very hot |
| 9 | 240°C | 220°C | 475°F | Very hot |
Printed charts differ by a few degrees at the edges. Gas mark 3 appears as 160°C in some tables and 170°C in others, because 325°F converts to 162.8°C. Gas mark ½ is sometimes listed as 130°C for a similar reason. None of these small differences will spoil a bake, but stick with one chart so your results stay consistent.
Conventional to fan oven converter
°C conventional= °C fanExact Fahrenheit equivalent: °F
How do you convert a conventional temperature to fan?
Take 20°C off the conventional figure. A recipe asking for 190°C needs 170°C fan; one asking for 150°C needs 130°C fan. The rule works across the normal cooking range because the gap comes from how heat reaches the food, not from the number on the dial.
If you are starting from a gas mark, find the conventional Celsius value first, then subtract 20°C. Gas mark 6 is 200°C, so the fan setting is 180°C. The worked example for the most common baking setting is in the guide to gas mark 4 in Celsius for fan ovens.
How do you convert a fan temperature to conventional?
Add 20°C to the fan figure. This matters if your oven has no fan, if the fan has failed, or if you prefer conventional heat for something like a rich fruit cake. A recipe that says 160°C fan becomes 180°C conventional, and 200°C fan becomes 220°C conventional.
Which oven setting are you actually using?
Check the symbol on the function dial, because many ovens offer more than one type of heat. Symbols vary between brands, so confirm them in the manual, but the common ones are:
- Conventional (top and bottom heat): a line at the top and a line at the bottom of a square. Use the conventional column.
- True fan or fan oven: a fan inside a circle, showing the ring element around the fan. Use the fan column.
- Fan-assisted: a fan with top and bottom lines. The elements heat while the fan stirs the air. Most manuals treat this like fan cooking, sometimes with a smaller reduction.
- Gas oven: no adjustment at all. Use the gas mark the recipe gives.
When should you not take 20°C off?
Do not reduce a temperature that is already labelled fan. Modern UK recipes, supermarket packaging and many cookbooks print both figures, such as “200°C, 180°C fan, gas 6”. Reducing the fan figure a second time leaves the oven 40°C too cool, which is the most common reason for pale pastry and underdone middles.
American recipes are a separate case. A US recipe at 350°F almost always assumes a conventional oven, so convert to 180°C first and then subtract 20°C for a fan. The Celsius to Fahrenheit converter gives the exact figure for any number that is not on the chart.
Tips for getting fan oven bakes right
- Check early. Look at the food five to ten minutes before the recipe time, as some fans run more fiercely than others.
- Use the extra shelves. Fan heat is more even from top to bottom, which is why it suits batch baking on two or three shelves at once.
- Cover delicate tops. If a cake browns before the middle sets, lay a sheet of foil loosely over it for the last part of baking.
- Test your thermostat. An inexpensive oven thermometer on the middle shelf shows whether your dial reads high or low, which matters more than any chart.
Frequently asked questions
How much lower should a fan oven be?
About 20°C lower than a conventional oven. Some manufacturers suggest a smaller reduction for their models, so check your oven manual if results seem off.
What is 180°C conventional in a fan oven?
180°C conventional is 160°C in a fan oven. This is gas mark 4, or 350°F in an American recipe.
What is 200°C fan in a conventional oven?
200°C fan is 220°C in a conventional oven, which is gas mark 7 or 425°F.
Do I need to change the cooking time in a fan oven?
Usually not, if you have already lowered the temperature by 20°C. Start checking a little early, because fan strength varies between ovens.
Do American recipes use fan temperatures?
Most American recipes give a conventional temperature in Fahrenheit. Convert it to Celsius, then subtract 20°C if you are using a fan oven.
Sources
- Which?: oven temperature conversion guide
- Smeg UK: oven temperature conversions
- National Physical Laboratory for the Celsius and Fahrenheit scales