Precision unit conversion
Why Gas Mark doesn't convert with a simple formula, and how to get your oven temperature right whichever scale your recipe or cooker uses.
If you've ever picked up a US baking blog and found a recipe calling for "350°F" with no Gas Mark or Celsius equivalent in sight, you'll know how easy it is to end up guessing at oven temperatures. The reverse is just as common for anyone using an older UK cooker that only shows Gas Mark numbers, trying to follow a modern recipe written in Celsius.
Length and weight conversions are just multiplication — 1 inch is always 25.4mm, no matter what value you start with. Gas Mark doesn't work that way. It was set by cooker manufacturers against a series of fixed reference points rather than a mathematical formula, so an accurate conversion means interpolating between those published points rather than applying one multiplier across the whole range.
| Convert | Result |
|---|---|
| Gas Mark ¼ | 110°C / 225°F — very cool, for slow-cooking and drying |
| Gas Mark 1 | 140°C / 275°F — cool, for meringues |
| Gas Mark 3 | 170°C / 325°F — warm, for slow roasting |
| Gas Mark 4 | 180°C / 350°F — moderate, the most common baking temperature |
| Gas Mark 6 | 200°C / 400°F — moderately hot, for roasting |
| Gas Mark 8 | 230°C / 450°F — very hot, for bread and pizza |
Most Gas Mark and Celsius figures in recipe books assume a conventional oven. If your oven is a fan (convection) oven, the general rule of thumb used across most UK cookbooks is to reduce the stated Celsius temperature by around 20°C, since a fan circulates hot air more efficiently and cooks faster at the same nominal setting. It's worth checking your specific oven's handbook too, since the exact adjustment can vary by 10–20°C between manufacturers.
When following a US recipe, remember Fahrenheit numbers are always larger than the equivalent Celsius figure for baking-range temperatures, so if you see something like "180" written without a unit, check the source — 180°F is barely warm, while 180°C is a standard moderate oven. And if a recipe just says "moderate oven" with no number at all, that's shorthand for roughly Gas Mark 4 / 180°C / 350°F.
Put this into practice with the live tool.
Open Oven Temperature & Gas Mark converter →180°C is Gas Mark 4 — one of the most commonly used baking temperatures, described as a "moderate" oven.
A common rule of thumb is to reduce the stated Celsius figure by about 20°C for a fan/convection oven, though it's worth checking your oven's own handbook since the exact adjustment varies by make.