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Oven Temperature Conversions: Fahrenheit, Celsius, and Gas Mark

Recipes from different countries and different eras describe oven heat in three different systems. Here is how they line up.

Fahrenheit and Celsius, roughly

A rough mental conversion: subtract 32 from the Fahrenheit number, then divide by 2 (the exact formula divides by 1.8). A 350°F oven, common for baking, is close to the exact 177°C, usually rounded to 180°C on dial ovens.

What a gas mark number means

Gas mark is a numbering system used mainly in the UK and some Commonwealth countries for gas ovens, running roughly from mark 1 (lowest) to mark 9 (highest), with each step corresponding to a fixed temperature rather than a proportional increase.

Common gas mark equivalents

Gas mark 4 is about 350°F / 180°C, a very common "moderate" baking temperature. Gas mark 6 is about 400°F / 200°C, a common roasting temperature. Gas mark 2 is about 300°F / 150°C, a low, slow-cooking temperature.

Heat-level names in older recipes

Older or simplified recipes sometimes skip numbers entirely and use words like "slow" (roughly 300-325°F), "moderate" (roughly 350-375°F), and "hot" (roughly 400-450°F) — imprecise by design, but close enough for many traditional dishes.

Adjusting for a fan (convection) oven

Recipes written for a conventional oven typically run hotter than needed in a fan/convection oven, since the moving air cooks food faster. A common rule of thumb is to lower the set temperature by about 20°C (or about 25°F), or reduce cooking time slightly, when using a fan setting.

Why gas mark does not scale like degrees

Unlike Fahrenheit or Celsius, where the numbers scale in even, ongoing units, gas mark was built around the physical settings of older gas oven dials, so its numbering is not proportional in the same way — mark 6 is not simply "twice as hot" as mark 3, it is just the next fixed setting up.

Oven thermostats are not perfectly accurate

Many home ovens run several degrees hotter or cooler than their dial setting indicates, sometimes enough to affect baking results. An inexpensive oven thermometer placed inside the oven is a more reliable way to confirm actual temperature than trusting the dial or display alone.

Frequently Asked Questions

Is gas mark only used for gas ovens?

It originated with gas ovens, but the numbering system is now printed on many recipes and even some electric oven dials in the UK and similar markets purely as a reference scale, regardless of the oven's actual heat source.

Why do US and UK recipes list different temperatures for the "same" dish?

Partly unit differences (Fahrenheit vs. Celsius or gas mark) and partly genuine differences in oven design and testing conventions between regions, so converting the number is necessary but not always sufficient — cooking times may still need slight adjustment.