400°F — all four oven scales
The exact conversion is (°F − 32) × 5/9, so 400°F works out to 204.4°C. Recipe writers round this to 200°C — the long-standing pairing that also maps to gas mark 6 — because no home oven holds a fraction of a degree and no dial displays one. That's 4.4°C of rounding, the kind every published conversion chart builds in.
For a conventional recipe in a fan (convection) oven, use 180°C — the standard UK adjustment is conventional minus 20°C (a 36°F difference), because moving air transfers heat faster than still air; the oven isn't hotter than its dial, it just cooks faster at the same setting. Hoover also says long cooking times can be shortened by up to 10 minutes per cooking hour — check the food is cooked. Bake times are otherwise unaffected by converting between scales: 200°C and 400°F are the same setting.
Where 400°F sits on the chart
| °F | °C | Fan °C | Gas mark | Descriptor |
|---|---|---|---|---|
| 350°F | 180°C | 160°C | 4 | Moderate |
| 375°F | 190°C | 170°C | 5 | Moderately hot |
| 400°F | 200°C | 180°C | 6 | Moderately hot |
| 425°F | 220°C | 200°C | 7 | Hot |
| 450°F | 230°C | 210°C | 8 | Hot |
See the full chart on the oven temperature converter → · Fan oven conversion chart →
What bakes at this temperature
400°F / 200°C is the territory of crusty breads, choux pastry and biscuits. Home ovens cycle above and below their set point and many run hot or cold from the factory — a standalone oven thermometer on the middle rack tells you more than any conversion chart can.