Stove Temperature Converter

Understanding Oven Temperature Systems

Recipes from around the world use three different systems to describe oven temperatures: Celsius (used in most countries), Fahrenheit (used in the United States), and gas mark (used primarily in the United Kingdom and some Commonwealth countries). Converting between them is essential when following international recipes.

Gas Mark System:

The gas mark system was introduced in 1943 by the British gas company Parkinson Cowan. Gas marks range from 1/4 (very cool) to 10 (very hot). Each gas mark increment represents a 25 degree Fahrenheit (approximately 14 degree Celsius) increase in temperature.

Conversion Formulas:

Fahrenheit = (Gas Mark × 25) + 250 (for gas marks 1 and above) Celsius = (Fahrenheit - 32) × 5/9 Gas Mark = (Fahrenheit - 250) / 25 (for temperatures 275F and above)

For low gas marks (1/4 and 1/2), the formula is approximate. The exact values are:

• Gas Mark 1/4 = 225F = 107C
• Gas Mark 1/2 = 250F = 121C

Complete Gas Mark Conversion Table:

Two Celsius columns, and the difference between them is the single most confusing thing about oven temperatures. The exact column is the arithmetic conversion of the Fahrenheit figure. The dial column is what a European oven is actually marked with, because manufacturers use round numbers and no dial in the world has 177 on it.

The dial column is not a rounding of the exact one, quite. At Gas Mark 9 the two are six degrees apart in opposite directions from anything you would call rounding. That is because the metric dial scale was set independently in round 10-degree steps rather than derived from the Fahrenheit figures, so the two systems drift against each other as they climb.

For cooking, the difference is irrelevant: an ordinary domestic oven swings by 15 to 20 degrees either side of its setpoint as the element cycles, which is far more than any of this. Set the dial to the round number and stop worrying.

Common Baking Temperatures:

Fan Oven Adjustment, and why two rules are in circulation

A fan-assisted (convection) oven moves hot air across the food instead of relying on it drifting, so it cooks faster at the same setting and you have to turn it down. Everyone agrees on that. What they do not agree on is by how much, and there are two conventions that are not equivalent to each other:

• The UK rule: reduce by 20°C. Gas Mark 6, a 200°C dial, becomes 180°C fan.
• The US rule: reduce by 25°F. 400°F becomes 375°F.

Those look similar and are not. 20°C is a 36°F reduction, while 25°F is only a 14°C reduction, so the UK rule is more than twice as aggressive. A recipe converted with the wrong one will be noticeably out.

This page uses the 20°C rule, because that is what fan-oven manufacturers print in their own manuals and it matches the “minus 20” mark on most European dials. If you are following an American recipe on an American convection oven, use its 25°F figure instead and expect the two to disagree; neither is wrong, they are just different traditions.

Whichever you use, the real answer is a thermometer. Domestic ovens are commonly 15 to 25 degrees off their own dial, and a cheap oven thermometer settles more baking arguments than any conversion table.