You're cooking a British recipe that calls for "Gas Mark 6." Or an Italian one specifying 180°C. Or you bought a French cookbook converted poorly to English with the temperatures still in Celsius. Three oven temperature scales exist, and switching between them confuses every cook eventually. Here's the full picture.
The three scales
- Fahrenheit (°F): United States standard. Range 200°F (slow) to 550°F (broil).
- Celsius (°C): Most of the world. Range 90°C (slow) to 290°C (broil).
- Gas Mark: British scale, 1/4 to 9. Used on gas ovens; rarely on electric ones in modern Britain.
F ↔ C conversions
The exact formula:
- F = C × 9/5 + 32
- C = (F − 32) × 5/9
For mental approximation, use: C ≈ (F − 30) ÷ 2. Off by a few degrees, but fine for ovens.
Common oven temperatures
| Description | °F | °C | Gas Mark |
|---|---|---|---|
| Very low (slow cook) | 250°F | 120°C | 1/2 |
| Low | 275°F | 135°C | 1 |
| Slow | 300°F | 150°C | 2 |
| Moderate-low | 325°F | 165°C | 3 |
| Moderate | 350°F | 180°C | 4 |
| Moderate-high | 375°F | 190°C | 5 |
| Hot | 400°F | 200°C | 6 |
| Very hot | 425°F | 220°C | 7 |
| Very hot | 450°F | 230°C | 8 |
| Extremely hot | 475°F+ | 245°C+ | 9 |
Gas Mark logic
Each Gas Mark step is roughly 25°F. The scale is designed for British gas ovens, which used to have only crude markings rather than digital displays. Gas Mark 4 = "moderate" — most baking happens here. Gas Mark 7 = "hot" — what bread bakes at.
The scale extends below 1 with fractional marks: Gas Mark 1/4 (225°F) and 1/2 (250°F) for low-and-slow cooking like meringues or slow-roasted meats.
Fan vs conventional ovens
Fan (convection) ovens distribute heat more efficiently. Recipes written for conventional ovens need a temperature reduction:
- Reduce by 25°F when using a fan oven instead of conventional
- Or 20°C in metric terms
So a recipe calling for 350°F conventional becomes 325°F fan. A 180°C recipe becomes 160°C fan.
The reduction applies to most baking. Some recipes (like roasting where you want a brown crust) keep the higher temperature even with a fan.
Bake time on fan ovens
Fan ovens not only run effectively hotter — they also cook faster. With the temperature reduction, bake times stay roughly the same for cakes and bread. For roasts, reduce time by ~10–15% on top of the temperature drop.
Oven calibration: the elephant in the kitchen
Every oven dial is approximate. Real internal temperatures often differ from the set dial by 25–50°F. An oven thermometer ($10) hung on the middle rack tells you the truth. Once you know your oven runs 25°F hot or 30°F cold, adjust accordingly forever.
Older ovens drift over years. New ones come with factory calibration but may need adjustment after the first major use. Most ovens have a calibration mode (consult the manual) where you can offset the displayed temperature by ±35°F.
Hot spots
Even a perfectly-calibrated oven has hot and cold spots. Rotate baking sheets halfway through; rotate cakes if you bake on multiple racks. Some bakers test by spreading sliced bread across the rack and toasting at 350°F for a few minutes — uneven browning shows the hot/cold pattern.
Special temperatures
"Low and slow": 200°F (95°C) for things like overnight pulled pork or slow-roasted tomatoes. Most ovens go this low; some don't.
"Pizza temperature": 500°F+. Many home ovens max out at 500°F. Pizza stones help replicate higher restaurant-oven temperatures.
"Broil": 550°F+. Direct top-element heat for browning.
Why exact temperature matters less than you think
Real ovens vary by ±25°F from their dial setting — sometimes more in older units. So a recipe that calls for 350°F is really fine anywhere from about 335 to 375. The conversion to Celsius (177°C) doesn't need pinpoint accuracy. Round to the nearest 5°C and your bake will be indistinguishable from the "correct" value.
Where exactness matters: very temperature-sensitive recipes like macarons (300°F precisely) and meringues (200°F precisely). For these, an oven thermometer plus the calibration adjustment gets you closer than any conversion math.
The "no-thermometer test"
Old-school bakers tested oven heat by holding a hand near the open door:
- Comfortable for 5+ seconds: low oven (~300°F)
- Comfortable for 3 seconds: moderate (~350°F)
- Uncomfortable in 1 second: hot (~425°F)
- Pull back instantly: very hot (450°F+)
Crude but useful when your oven thermometer is missing.
Tools to convert quickly
Our oven temperature converter handles all three scales plus fan-oven adjustment in one keystroke. Useful when an international recipe doesn't specify or when you want to translate between conventional and convection mode.