How to use this calculator
Enter the temperature from your recipe in whichever form it is written. The Fahrenheit and Celsius fields show the conventional (no fan) setting; the fan field shows the equivalent for a convection or fan-assisted oven, and the gas mark field the British gas cooker setting. Choose the convection rule you prefer: US recipes and oven manuals usually reduce by 25 °F, UK and European recipes by 20 °C.
Working from a British recipe that says “gas mark 6 or 180 °C fan”? Type 6 in the gas mark field, or 180 into the fan field with the unit set to °C, and the conventional settings appear.
The formula
- T_F
- conventional oven, fahrenheit
- T_C
- conventional oven, celsius
- T_fan
- fan / convection oven
- GM
- gas mark
Worked example
An American recipe says to bake at 350 °F. What is that in Celsius, in a convection oven and on a British gas cooker?
- °C = (350 − 32) × 5/9 = 176.7 °C (recipes round to 180 °C).
- Convection: reduce by 25 °F → 325 °F.
- Gas mark = (350 − 250) ÷ 25 = 4.
350 °F is 177 °C, 325 °F with the fan, or gas mark 4.
Oven temperature chart
| Gas mark | °F | °C | Description |
|---|---|---|---|
| ¼ | 225 | 107 | Very cool |
| ½ | 250 | 121 | Very cool |
| 1 | 275 | 135 | Cool |
| 2 | 300 | 149 | Cool |
| 3 | 325 | 163 | Moderate |
| 4 | 350 | 177 | Moderate |
| 5 | 375 | 191 | Moderately hot |
| 6 | 400 | 204 | Hot |
| 7 | 425 | 218 | Hot |
| 8 | 450 | 232 | Very hot |
| 9 | 475 | 246 | Very hot |
Celsius values here are exact conversions; recipes usually round them to the nearest 10 °C.
Assumptions and limits
- Gas marks follow the common British scale (mark 1 = 275 °F, 25 °F per mark). Individual cookers vary by ±10 °C; an oven thermometer is the only way to know.
- The fan adjustment is a rule of thumb; some modern convection ovens adjust automatically — check the manual.
Frequently asked questions
What is 180 °C in Fahrenheit?
356 °F, usually treated as 350 °F in recipes. 200 °C is 392 °F (400 °F), and 220 °C is 428 °F (425 °F).
Do I need to lower the temperature for a fan oven?
Usually yes: a fan transfers heat faster, so recipes written for conventional ovens are reduced by about 25 °F or 20 °C, or the time is shortened.
What gas mark is 200 °C?
Gas mark 6 (400 °F, 204 °C).
Sources
- NIST — Temperature unit conversions (SP 811, Appendix B)
- USDA FSIS — Safe minimum internal temperature chart
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