Gas mark 2 — 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 2 lands at 300°F / 150°C, which the traditional cookbook descriptors call a slow oven. If your recipe is older or British and your oven is not, these two numbers are the whole translation.
For a conventional recipe in a fan (convection) oven, use 130°C — the standard UK adjustment is conventional minus 20°C (a 36°F difference), because moving air transfers heat faster than still air; the oven isn't hotter than its dial, it just cooks faster at the same setting. Hoover also says long cooking times can be shortened by up to 10 minutes per cooking hour — check the food is cooked. Bake times are otherwise unaffected by converting between scales: 150°C and 300°F are the same setting.
Where gas mark 2 sits on the chart
| °F | °C | Fan °C | Gas mark | Descriptor |
|---|---|---|---|---|
| 250°F | 120°C | 100°C | ½ | Very slow |
| 275°F | 140°C | 120°C | 1 | Slow |
| 300°F | 150°C | 130°C | 2 | Slow |
| 325°F | 160°C | 140°C | 3 | Moderately slow |
| 350°F | 180°C | 160°C | 4 | Moderate |
See the full chart on the oven temperature converter → · Fan oven conversion chart →
What bakes at this temperature
300°F / 150°C is the territory of rich fruit cakes and other long, slow bakes. Home ovens cycle above and below their set point and many run hot or cold from the factory — a standalone oven thermometer on the middle rack tells you more than any conversion chart can.