Oven temperature converter
Convert oven temperatures between Celsius, Fahrenheit, gas mark and fan/convection, with the descriptive terms old cookbooks use and a full chart.
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Whole numbers are fine — ovens are not that precise anyway.
Typically used for: The default: sponge cakes, cookies, most bakes.
°F = (°C × 9/5) + 32 °F = (180.0 × 9/5) + 32 = 350.0 °F fan °C = conventional °C − 20 fan °C = 180.0 − 20 = 160.0 °C gas mark → °F = 25 × (mark + 10) for marks 1 to 9 nearest mark to 180 °C is 4 (180 °C / 350 °F)
| Gas mark | Conventional °C | Fan °C | °F | Described as |
|---|---|---|---|---|
| 1/4 | 110 °C | 90 °C | 225 °F | Very cool |
| 1/2 | 120 °C | 100 °C | 250 °F | Very cool |
| 1 | 140 °C | 120 °C | 275 °F | Cool |
| 2 | 150 °C | 130 °C | 300 °F | Cool |
| 3 | 170 °C | 150 °C | 325 °F | Warm |
| 4 | 180 °C | 160 °C | 350 °F | Moderate |
| 5 | 190 °C | 170 °C | 375 °F | Moderately hot |
| 6 | 200 °C | 180 °C | 400 °F | Moderately hot |
| 7 | 220 °C | 200 °C | 425 °F | Hot |
| 8 | 230 °C | 210 °C | 450 °F | Hot |
| 9 | 240 °C | 220 °C | 475 °F | Very hot |
| 10 | 260 °C | 240 °C | 500 °F | Very hot |
Four scales for one dial
An oven temperature can be written four ways, and a recipe will use whichever its author grew up with: degrees Fahrenheit in the US, degrees Celsius almost everywhere else, gas marks in Britain and Ireland, and — separately from all three — a fan or convection setting that is about 20 °C lower than the conventional number for the same result.
Generic temperature converters handle the first two and miss the two that actually cause ruined dinners.
The fan oven rule
A fan (convection) oven circulates air, which strips away the insulating boundary layer that sits against food in still air. Heat therefore transfers faster at the same air temperature, and the standard compensation is to reduce the setting by 20 °C, or about 25–30 °F.
So 180 °C conventional is 160 °C fan. 200 °C conventional is 180 °C fan. If a recipe says "180 °C (160 °C fan)" it has already done this for you; if it gives one number and you have a fan oven, subtract.
Cooking time drops too — typically by around 10% — and the effect is strongest for anything with an exposed surface. Fan is excellent for roasting and batch baking, and can be too aggressive for delicate custards, soufflés and rich fruit cakes, which is why many ovens let you switch it off.
Gas marks
Above mark 1 the ladder is a clean formula: °F = 25 × (mark + 10). Mark 4 is 25 × 14 = 350 °F. Mark 7 is 425 °F. Below mark 1 the pattern breaks, with mark 1/2 at 250 °F and mark 1/4 at 225 °F, because those settings were added later for slow cooking and meringues.
Gas ovens also run with a stronger vertical temperature gradient than electric ones — the top shelf can be a full gas mark hotter than the bottom. British recipes that specify a shelf position are not being fussy.
The descriptive terms
| Term | Conventional °C | °F |
|---|---|---|
| Very cool / very slow | 110–120 | 225–250 |
| Cool / slow | 140–150 | 275–300 |
| Warm | 170 | 325 |
| Moderate | 180 | 350 |
| Moderately hot | 190–200 | 375–400 |
| Hot | 220–230 | 425–450 |
| Very hot | 240–260 | 475–500 |
Recipes written before ovens had thermostats used these terms exclusively, and they still turn up in reprints of older cookbooks.
Your oven is probably lying
Domestic ovens routinely run 10–20 °C away from their dial, and the thermostat cycles the element on and off, so the actual air temperature swings around the set point rather than holding it. An oven thermometer costs a few pounds and will tell you more about your baking than any conversion chart — including which shelf is the hot one.
Preheat properly, too. The light going out means the air is up to temperature; the walls and the shelves are not, and a pizza stone can take forty minutes to catch up.
Questions
What is 350 °F in Celsius for a fan oven?
350 °F is 177 °C, which every recipe rounds to 180 °C. In a fan oven, drop it to 160 °C — the standard 20 °C reduction.
What is gas mark 4?
180 °C conventional, 160 °C fan, 350 °F. It is the default setting for most cakes and biscuits, and the mark British recipes reach for by reflex.
Why do fan ovens need a lower temperature?
Moving air strips away the insulating boundary layer of still air around the food, so heat transfers faster at the same air temperature. The 20 °C reduction compensates. Some manufacturers say 25 °C; the difference is within the accuracy of a domestic oven anyway.
Is there a formula for gas marks?
Above mark 1, yes: °F = 25 × (mark + 10). Gas mark 4 is 25 × 14 = 350 °F. Below mark 1 the ladder breaks down, with mark 1/2 at 250 °F and mark 1/4 at 225 °F.
Is my oven actually at the temperature it says?
Very likely not. Domestic ovens routinely run 10–20 °C off their dial and swing further as the thermostat cycles. A cheap oven thermometer is worth more than any conversion chart.