Precision unit conversion
UK recipes and cookers often give oven temperatures as a "Gas Mark" number rather than a degree value, which is meaningless if your oven only shows Celsius or Fahrenheit — or if you're following a US recipe that skips Gas Mark entirely.
Gas Mark is a UK standard scale, historically tied to the gas pressure/flow settings on older gas cookers, and it doesn't follow a simple straight-line formula against Celsius or Fahrenheit the way, say, kilometres and miles do. Instead, it follows a set of standard published reference points, shown in full below.
| Convert | Result |
|---|---|
| Gas Mark ¼ | 110°C / 225°F (very cool) |
| Gas Mark ½ | 120°C / 250°F |
| Gas Mark 1 | 140°C / 275°F (cool) |
| Gas Mark 2 | 150°C / 300°F |
| Gas Mark 3 | 170°C / 325°F (warm) |
| Gas Mark 4 | 180°C / 350°F (moderate) |
| Gas Mark 5 | 190°C / 375°F |
| Gas Mark 6 | 200°C / 400°F (moderately hot) |
| Gas Mark 7 | 220°C / 425°F (hot) |
| Gas Mark 8 | 230°C / 450°F (very hot) |
| Gas Mark 9 | 240°C / 475°F |
If your oven is a fan (convection) oven, most UK recipe books recommend reducing the stated Celsius temperature by about 20°C, since fan ovens circulate heat more efficiently — check your cooker's handbook, as this can vary by make and model.
The full converter switches directly between Gas Mark, Celsius and Fahrenheit, so you can follow any recipe regardless of which scale it uses.
Open Oven Temperatures converter →Gas Mark 4 is 180°C, which is 350°F. It's one of the most common UK baking temperatures.
Gas Mark 6 is 200°C, or 400°F — a moderately hot setting often used for roasting.
Many UK recipes are written for conventional (non-fan) ovens, so if you're using a fan/convection oven, a common rule of thumb is to reduce the Celsius figure by about 20°C — check your oven's manual, since the exact adjustment varies.
Gas Mark was originally set by cooker manufacturers against fixed reference points rather than a mathematical scale, so converting it accurately means interpolating between those published reference points rather than applying one multiplier.