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Gas Mark

General

UK Gas Oven Temperature Scale

A numbered scale (¼ to 9) used on UK gas ovens to indicate temperature, printed on most British recipes instead of — or alongside — Celsius and Fahrenheit.

Definition

Gas Mark is a numbered temperature scale, running from ¼ to 9, used on gas ovens in the United Kingdom and historically across much of the Commonwealth. It dates back to the dial settings on early British gas cookers, which were marked with numbers rather than a direct temperature reading, and the convention stuck even as ovens became more precise.

Unlike Celsius or Fahrenheit, gas mark doesn't increase by a fixed number of degrees per step — the gap between gas mark 1 and 2 is smaller than the gap between gas mark 6 and 7, for example. This makes converting gas mark to a standard temperature scale a lookup-table problem rather than a simple formula, which is why dedicated conversion tools like the Oven Temperature Converter use a reference chart rather than a single equation.

Most UK recipes today print gas mark alongside Celsius and Fahrenheit, since ovens vary in which scale they display.

Formula

There is no single formula linking gas mark to Celsius — the relationship is defined by a fixed reference table rather than a mathematical equation:

Gas Mark °C °F
¼ 110 225
1 140 275
4 180 350
6 200 400
9 240 475

To convert, look up the matching row — interpolating between rows for values that fall in between.

Worked Example

A British recipe calls for "gas mark 5" to bake a sponge cake. Looking up the reference table, gas mark 5 corresponds to 190°C (375°F).

If you're using a fan-assisted oven, most manufacturers recommend reducing this by about 20°C, setting the oven closer to 170°C instead, to account for the more efficient heat circulation.

Key Things to Know

  • Not evenly spaced: the temperature difference between consecutive gas marks isn't constant, so simple proportional formulas don't work — always use a reference table.
  • Fan ovens run hotter: reduce the converted temperature by roughly 20°C, or one gas mark, when using a fan-assisted oven.
  • Still printed on UK recipes: even though many modern ovens default to Celsius, gas mark remains common on British cookbooks and older oven dials.
  • Use the Oven Temperature Converter for instant conversion in both directions, rather than memorising the reference table.

Frequently Asked Questions

Gas mark 4 is 180°C (350°F), one of the most commonly used settings for general baking such as cakes and biscuits. It sits roughly in the middle of the standard gas mark scale.
Gas mark was designed around the dial positions of early gas cooker thermostats, not as a linear mathematical scale, so the temperature gap between consecutive marks varies — some steps are 10°C, others are 20°C. This is different from Celsius and Fahrenheit, which both increase by a fixed amount per unit.
Many modern UK ovens display Celsius or Fahrenheit by default, but gas mark is still printed on oven dials in some homes and remains common in older and reprinted British recipes. Most UK cookbooks today print all three scales side by side to cover every oven type.
The scale runs from gas mark ¼ (110°C / 225°F), used for very slow cooking, up to gas mark 9 (240°C / 475°F), used for high-heat baking such as pizza. Marks below 1 are written as fractions (¼, ½) rather than whole numbers.
Fan ovens circulate heat more efficiently, so most manufacturers recommend reducing the equivalent temperature by about 20°C (or roughly one gas mark) compared to a conventional oven. Always check your specific oven's manual, since the adjustment can vary by model.