Gas Mark 9 — all four oven scales
Gas marks are the scale on British and Irish gas ovens: gas mark 1 is 275°F / 140°C and each whole mark up adds 25°F. Gas mark 9 lands at 475°F / 245°C, which the traditional cookbook descriptors call a very hot oven. If your recipe is older or British and your oven is not, these two numbers are the whole translation.
In a fan (convection) oven, use 225°C — the standard adjustment is conventional minus 20°C, because moving air transfers heat faster than still air. Make the temperature adjustment or shorten the bake time by about a quarter, never both. Bake times are otherwise unaffected by converting between scales: 245°C and 475°F are the same heat wearing different units.
Where gas mark 9 sits on the chart
| °F | °C | Fan °C | Gas mark | Descriptor |
|---|---|---|---|---|
| 375°F | 190°C | 170°C | 5 | Moderately hot |
| 400°F | 200°C | 180°C | 6 | Moderately hot |
| 425°F | 220°C | 200°C | 7 | Hot |
| 450°F | 230°C | 210°C | 8 | Hot |
| 475°F | 245°C | 225°C | 9 | Very hot |
See the full chart on the oven temperature converter →
What bakes at this temperature
475°F / 245°C is the territory of pizza, flatbreads and the hottest setting most home ovens reach. Remember that most home ovens swing ±25°F around their set point and many run permanently hot or cold — a standalone oven thermometer on the middle rack tells you more than any conversion chart can.