Oven temperature converter: °C, °F, gas marks and the fan adjustment
Type what your recipe says — Celsius, Fahrenheit or a gas mark — and get every other reading, including what to set on a fan oven. The exact math is honest (°F = °C × 9⁄5 + 32), and where UK sources disagree, the methodology section shows the disagreement instead of hiding it.
OvenMath temperature converter
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Key takeaways
- 180°C = 350°F ≈ gas mark 4 — the exact figure is 356°F, but dials snap to 25°F steps.
- Fan ovens: set 20°C lower as the common UK rule (Delia Online, BBC Good Food); Bosch officially says ~25°F (≈15°C). Real-world guidance spans 15–25°C — check early the first bake.
- Gas marks are a Fahrenheit system: gas mark G = (275 + 25 × (G−1))°F, so gas 4 = 350°F exactly.
- Never convert twice: a recipe that says “200°C fan” already had the reduction applied.
Methodology: where every number comes from
The converter has three layers, and each one is verifiable:
- Exact conversion: °F = °C × 9⁄5 + 32 and °C = (°F − 32) × 5⁄9. This is arithmetic, not opinion — 180°C really is 356°F.
- Dial convention: published charts round °F to the nearest 25 and °C to the nearest 10, because that's the resolution oven dials actually have. That is why charts pair 180°C with 350°F, and why this tool shows both the exact value and the dial value.
- Gas-mark spine: the gas mark system is defined in Fahrenheit — gas mark G corresponds to (275 + 25 × (G−1))°F, with quarter marks ¼ = 225°F and ½ = 250°F. For the Celsius pairings we cross-checked the two UK references bakers actually use: Delia Online's conversion table and BBC Good Food's conversion guide. They agree everywhere except gas 3 (Delia 170°C, BBC Good Food 160°C — 325°F is exactly 163°C) and we store the 165°C midpoint so that both published pairings map to gas 3. The chart page shows both values side by side.
- Fan adjustment: default −20°C, per Delia Online (“reduce the temperature by 20 degrees centigrade, or check the manufacturer's handbook”) and BBC Good Food's fan column, which is uniformly 20°C below conventional. Bosch's official convection guide publishes a smaller cut — about 25°F (≈15°C) — so the tool displays the full 15–25°C range and you can see all three readings.
Last verified: 2026-11-16 — sources: Delia Online, BBC Good Food, Bosch Home (official), all fetched live on that date.
Worked examples
Example 1: American recipe says 350°F — what gas mark?
Enter 350 with unit °F. Exact: 176.7°C. Dial convention:
180°C / 350°F, gas mark 4. If your oven is a fan oven, the tool shows
160°C fan (−20°C rule). That covers every dial type a UK or EU kitchen
can throw at a chocolate-chip cookie recipe.
Example 2: British recipe says 220°C / 200°C fan — you own a US oven
Enter 220 °C. Exact: 428°F; dial convention 425°F ≈ gas 7.
The fan figure the recipe prints (200°C) already includes the −20°C reduction — so on a
conventional US oven you bake at 425°F, not 400°F, and you never subtract twice.
Example 3: Old recipe says “gas mark ½”
Enter 0.5 with unit gas: that's 250°F / 120°C conventional,
~100°C fan — the very-cool zone used for drying meringues and slow-drying fruit.
Common anchors worth memorising
| Baking job | Conventional | Fan | Gas |
|---|---|---|---|
| Meringues / drying | 110–140°C | 90–120°C | ¼–1 |
| Rich fruit cake (long bake) | 140–150°C | 120–130°C | 1–2 |
| Cakes, brownies, biscuits | 180°C | 160°C | 4 |
| Bread, Yorkshire puddings | 200–220°C | 180–200°C | 6–7 |
| Hot oven: pizza, flatbreads | 230–240°C | 210–220°C | 8–9 |
The full table, with the two published Celsius values for gas 3 and the °F spine, lives on the oven temperature chart page.
Digital oven thermometer
Delia's team recommends one; ours agrees: the cheapest way to find out your oven runs 15°C hot is a £10 thermometer, not a ruined cake.
Check price →