Unit converter
Oven temperatures.
Gas mark to °C and °F, with fan oven settings alongside. Gas marks are not a unit — they are a numbered scale with a conventional temperature attached to each step — so they come from the chart below rather than from the converter, which handles °C and °F exactly.
| Gas mark | Conventional | Fan | Fahrenheit |
|---|---|---|---|
| ¼ | 110 °C | 90 °C | 225 °F |
| ½ | 120 °C | 100 °C | 250 °F |
| 1 | 140 °C | 120 °C | 275 °F |
| 2 | 150 °C | 130 °C | 300 °F |
| 3 | 160 °C | 140 °C | 325 °F |
| 4 | 180 °C | 160 °C | 350 °F |
| 5 | 190 °C | 170 °C | 375 °F |
| 6 | 200 °C | 180 °C | 400 °F |
| 7 | 220 °C | 200 °C | 425 °F |
| 8 | 230 °C | 210 °C | 450 °F |
| 9 | 240 °C | 220 °C | 475 °F |
- The °C and °F conversion is exact. Gas marks and fan settings are conventions, and the chart above is where they come from.
Definitions
- A gas mark is a numbered position on a dial, not a unit of temperature. The chart gives the temperature each mark is conventionally taken to mean; there is no formula, and manufacturers differ slightly.
- Between gas mark 1 and 9 the steps are close to 25 °F apart, which is why the Fahrenheit column is made of round numbers and the Celsius one is not.
- The fan column is the conventional setting less 20 °C, the rule UK recipes and oven manuals use. Some manufacturers say 15 °C and a few say 25 °C — check the manual before trusting the round number.
- A domestic oven's thermostat is typically within about 10–15 °C of the dial, and the air near the door is cooler than the air at the back. Converting to a tenth of a degree is arithmetic, not accuracy.
- °C and °F themselves are defined against the kelvin, so that part of the conversion is exact — the converter above handles it, and will happily work outside oven temperatures.
How it works
To convert an oven temperature from Celsius to Fahrenheit, multiply by 1.8 and add 32; to go the other way, subtract 32 first and then multiply by 5/9. That part is exact, and the converter above does it in both directions for any value you type.
Gas marks work differently. They are steps on a dial that a chart maps to temperatures, so the only honest way to convert one is to look it up — which is what the table does. Marks ¼ and ½ exist because the bottom of the range needed finer steps than whole numbers allowed.
For a fan oven, drop the conventional temperature by 20 °C and expect to shorten the time a little as well: moving air transfers heat faster, so the same dial setting cooks harder. A recipe that says 180 °C without qualification means a conventional oven.
Common questions this answers: what gas mark 4 is (180 °C conventional, 160 °C fan, 350 °F), what 180 °C is in a fan oven (160 °C), what 200 °C is in Fahrenheit (392 °F, usually rounded to 400 on a dial), and why the Fahrenheit column is rounder than the Celsius one.
- Temperature converter
- Celsius to Fahrenheit
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From the maker of Ans — a scientific calculator you can own. Same idea: a proper instrument, nothing in the way.