Oven Temperature Calculator
Oven temperatures across Celsius, Fahrenheit and gas mark — with the fan-forced adjustment and what it does to the cooking time.
The conversions are arithmetic, but the fan adjustment is the part recipes disagree about.
How the oven temperature calculator works
The conversions are arithmetic, but the fan adjustment is the part recipes disagree about. A fan oven circulates air, so it cooks faster at the same dial setting; the convention is to drop 20 °C, and most manufacturers agree.
Gas marks are not linear in any tidy way — they run in 25 °F steps from gas mark 1 at 275 °F. That is why converting them by formula gives numbers no recipe uses, and why this rounds to the marks that exist.
Formula: °F = °C × 9/5 + 32; fan = conventional − 20 °C
Worked examples
| Inputs | Fahrenheit | Note |
|---|---|---|
| 180 °C | 356 | 356 °F, gas mark 4 |
| A hot oven | 428 | gas mark 7 |
| A fan oven | 356 | the conventional equivalent is 200 °C |
FAQFrequently asked questions
How much do I reduce for a fan oven?
Twenty degrees Celsius is the standard adjustment. Some manufacturers say 15 or 25, so check your manual if results are consistently off.
What is gas mark 4?
About 180 °C or 350 °F — a moderate oven, and the most common setting in older recipes.
Why do gas marks not convert tidily?
Because they run in 25 °F steps from gas mark 1 at 275 °F. Converting exactly gives numbers no oven dial shows.
Does a fan oven cook faster as well as hotter?
Yes. At the same dial setting expect roughly a fifth less time, which is why the adjustment is usually applied to temperature rather than time.
Is my oven the temperature it says?
Often not. Domestic ovens commonly run 10 to 20 degrees out, and an oven thermometer is the cheapest cooking improvement available.
Where these figures come from
- US FDA — Safe Minimum Internal Temperatures — the internal temperatures the roasting calculator targets
- NIST SP 811 — Guide for the Use of the International System of Units — the exact weight and volume conversions used throughout
- Food Standards Australia New Zealand — food safety and labelling standards
Last checked: September 2026. Baking ratios follow standard baker's percentage practice; roasting guidance follows published safe internal temperatures.