Oven Temperature Converter (°C, °F, Gas Mark)
Convert an oven temperature between degrees Celsius, degrees Fahrenheit and gas mark, and adjust it for a fan oven. For example, 180 °C is 356 °F, which most American recipes write as 350 °F, and it is gas mark 4.
Last checked 11/11/2026. Sources: Which?: Oven temperature conversion table (gas marks 1 to 9 with fan temperatures; fan ovens about 20 °C lower); Wikipedia: Gas mark (gas marks ¼ and ½; marks rise 25 °F each; prints 170 °C for gas mark 3).
Guide
The formulas
The two scales meet at a simple rule: °F = °C × 9 ÷ 5 + 32, and the other way °C = (°F − 32) × 5 ÷ 9.
Worked example: 180 °C × 9 ÷ 5 + 32 = 356 °F. Going back, (350 − 32) × 5 ÷ 9 = 176.7 °C. Recipes and oven dials do not use these exact figures. They use a rounded dial value: 356 °F is written as 350 °F, and 176.7 °C is written as 180 °C. The converter shows both, and rounds the dial value to the nearest 10 °C or 25 °F.
Gas marks, and why they exist
A gas mark is a numbered setting on a gas oven, still common in British recipes. Gas mark 1 is 275 °F (140 °C on the usual chart), and each mark above it adds about 25 °F, which is 10 to 20 °C depending on the chart. Below gas mark 1 the steps are ½ and ¼. Gas marks belong to conventional gas ovens, so the converter gives the gas mark for the conventional temperature even when you set a fan oven.
Charts round, so they disagree a little. This page uses the Which? table for gas marks 1 to 9, where gas mark 3 is 160 °C. Wikipedia prints 170 °C for gas mark 3, and some cookery sites do too. If a temperature falls between marks, the converter shows the nearest mark. It does not invent fractions of a mark. For example, 200 °C is gas mark 6.
Fan oven or conventional?
A fan oven blows hot air around the oven, so food cooks faster and a recipe written for a conventional oven is usually set lower. The common rule is 20 °C lower (Which? gives the same figure). For a recipe in Fahrenheit the usual rule of thumb is 25 °F lower. These are not the same size: 20 °C is 36 °F. Both are editorial rules of thumb, not standards, so the converter uses 20 °C for recipes in °C and gas mark, and 25 °F for recipes in °F.
Worked example: a conventional recipe at 200 °C in a fan oven is 180 °C. A recipe written for a fan oven at 200 °C in a conventional oven is 220 °C. Recipe writers and oven makers differ, and many modern ovens make the adjustment themselves, so follow your oven’s manual and check food a little early.
Check with a thermometer
Ovens do not hold the number on the dial. They swing above and below it as the element cycles, and the dial can read several degrees off. A cheap oven thermometer on the middle shelf tells you what your oven really does. Use the converted number as the starting point.
Common questions
Is 180 the same as 350?
Nearly. 180 °C is exactly 356 °F and 350 °F is 176.7 °C. Recipes treat them as the same dial setting, and both are gas mark 4.
What is gas mark 4 in Celsius and Fahrenheit?
Gas mark 4 is 180 °C or 350 °F on the usual chart.
Should I lower the temperature for a fan oven?
If the recipe was written for a conventional oven, usually yes: about 20 °C (25 °F) lower. If the recipe already gives a fan temperature, use it as written. Many ovens make the adjustment automatically, so check your manual.
What if my temperature is between two gas marks?
The converter shows the nearest mark. Gas marks are set on a gas oven dial, so there is no mark in between.
Is the converted temperature exact?
The arithmetic is exact. The dial value is rounded because ovens and dials are not precise, and a thermometer is the real check.