Guide
Gas Mark conversion table (and why your British recipe says Mark 4)
The standard table, the history, the fan-oven adjustment.
British recipes from the 1950s to the 2010s call for oven temperatures in Gas Mark — a UK-specific scale numbering oven temperatures from ¼ (very slow) to 9 (very hot). For cooks outside the UK, or anyone using a modern electric oven labelled in °C or °F, the conversion is essential and rarely complicated. Here’s the full table.
The standard table
| Gas Mark | °F | °C | Description |
|---|---|---|---|
| ¼ | 225 | 110 | Very slow / dehydrating |
| ½ | 250 | 120 | Very slow / slow-roasting |
| 1 | 275 | 135 | Slow / slow-cooking |
| 2 | 300 | 150 | Slow / casseroles |
| 3 | 325 | 165 | Moderately slow |
| 4 | 350 | 180 | Moderate (the default for most baking) |
| 5 | 375 | 190 | Moderate / muffins, scones |
| 6 | 400 | 200 | Moderately hot / pies |
| 7 | 425 | 220 | Hot / roasting |
| 8 | 450 | 230 | Very hot / pastry |
| 9 | 475 | 246 | Very hot / pizza, bread crust |
The pattern
From Mark 1 to Mark 9, each step is 25°F (~14°C). So if you memorise just one anchor — Mark 4 = 350°F = 180°C — you can derive everything else by adding or subtracting 25°F per mark. This is also the cleanest way to interpolate non-integer values: Mark 4½ = 362°F.
Where Gas Mark came from
Introduced in the 1940s by British gas-appliance manufacturers as a standardised oven dial labelling system. The numbering was deliberately disconnected from any physical temperature unit — the goal was a numeric scale that wouldn’t invite second-guessing about calibration. By the 1960s every UK gas oven shipped with Gas Mark labels; British cookbooks followed the convention until well into the 2000s.
Why your recipe might still say Mark 4 in 2026
Most modern UK ovens are electric and labelled in °C, but cookbooks tend to outlive appliances. Mary Berry, Delia Smith, Nigella Lawson, and Jamie Oliver all wrote bestsellers specifying Gas Marks; their recipes get scanned, reblogged, and reprinted indefinitely. If your recipe is British and pre-2010, expect Gas Marks; if it’s newer, expect either Gas Marks or °C with both listed.
The fan-oven adjustment
Fan-assisted (convection) ovens cook ~20°C hotter than conventional at the same dial setting because the moving air transfers heat to food faster. Standard adjustment when converting a Gas Mark recipe for a fan oven:
- Subtract one Gas Mark, OR
- Subtract 20°C from the °C equivalent, OR
- Subtract 25°F from the °F equivalent.
Some modern recipes already specify the fan-oven temperature — check whether the recipe says “fan” before adjusting.
The cleanest workflow
- Look up the Gas Mark in the table above.
- If your oven is fan-assisted, drop one Gas Mark.
- Use the resulting °C or °F number on your oven.
- Verify with an oven thermometer if you’re baking something delicate (souffles, macarons, sourdough).
Or skip the mental math entirely and use our oven temperature converter — all three scales, fan-oven mode coming in a future update.
Frequently asked questions
- Why are some Gas Marks fractional (¼, ½)?
- Pre-1980s gas ovens couldn't reliably hold low temperatures, so the ¼ and ½ marks were introduced for dehydrating fruit, slow-roasting, and overnight cooking. Modern recipes use them rarely; the dial still has them on most UK gas ovens.
- Does Gas Mark mean the same on every oven?
- Approximately. The numbering was standardised in the 1950s and most UK gas appliances follow the same scale within ±5°F per mark. Cheaper ovens drift more; an oven thermometer is the only way to know your specific oven's calibration.
- How do I adjust for a fan-assisted oven?
- Reduce the temperature by about 20°C (or 25°F, or one Gas Mark) compared to a conventional oven. Some recipes already specify the fan temperature — check before adjusting.
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Published May 15, 2026