Gas mark

Gas mark is a temperature scale used on gas ovens in the UK and Ireland, and in many British recipes. It runs from ¼ (very cool) to 9 (very hot). Most modern recipes give gas marks next to Celsius and Fahrenheit, often written as "180°C, gas 4".

How to use it

From gas mark 1 upward, each step adds about 10 to 20°C (25°F).

Gas mark	Celsius	Fahrenheit	Description
¼	110°C	225°F	Very cool
½	120°C	250°F	Very cool
1	140°C	275°F	Cool
2	150°C	300°F	Cool
3	170°C	325°F	Moderate
4	180°C	350°F	Moderate
5	190°C	375°F	Moderately hot
6	200°C	400°F	Hot
7	220°C	425°F	Hot
8	230°C	450°F	Very hot
9	240°C	475°F	Very hot

Gas mark 4 is the one you will see most, for cakes, cookies (biscuits in the UK) and crumbles. Gas mark 6 and 7 are for roasting.

Gas ovens heat unevenly. The top shelf is usually hotter than the bottom, often by about one gas mark. Use that: put things that need more heat high up and gentle bakes low down. An oven thermometer on the middle shelf shows you what your oven really does.

Common mistakes

• Turning down a gas mark for a fan. Gas ovens do not usually have a fan, so a gas mark already means conventional heat. Only lower the heat if you are using a fan oven and converting from gas.
• Treating gas mark ¼ and ½ as off. They are low but real settings, used for drying meringues and slow-cooking.
• Opening the door too often. Gas ovens lose heat quickly and take a while to recover.

In recipes

You will see "Preheat the oven to 200°C/180°C fan/gas 6", "gas mark 4" and "gas 3". Older British cookbooks may give only gas marks, so keep the table handy.

Where it comes from

The scale comes from a thermostat for gas ovens introduced in Britain in the 1920s. The dial was numbered instead of marked in degrees, and the numbers stuck.