Oven Temperature Conversion: Fahrenheit, Celsius, and Gas Mark
The full Fahrenheit-to-Celsius-to-Gas Mark oven temperature table, why gas mark isn't a linear scale, how to adjust for fan/convection ovens, and a note on altitude adjustments.
Oven temperature conversion trips people up more than almost any other kitchen conversion because it isn't really one conversion — it's three overlapping systems (Fahrenheit, Celsius, and UK Gas Mark) plus a fourth variable, whether the oven is fan-assisted/convection or conventional, that changes the effective temperature regardless of what the dial says. Fahrenheit-to-Celsius is straightforward math, but Gas Mark is not simply Celsius relabeled — it's an older British scale with its own non-linear numbering that happens to roughly track Celsius in 25-degree steps at the low end but compresses at the high end. Getting this wrong is a common reason recipes from a different country underbake, overbake, or brown unevenly even when every ingredient was measured correctly. This guide gives you the accurate full table and the two adjustments — convection and altitude — that most conversion charts leave out.
Fahrenheit to Celsius: the exact formula
°C = (°F − 32) × 5/9, and the reverse, °F = (°C × 9/5) + 32. For baking purposes, most conversions are rounded to the nearest 5°C: 325°F = 163°C (rounded to 160°C or 165°C), 350°F = 177°C (rounded to 175°C or 180°C), 375°F = 191°C (rounded to 190°C), 400°F = 204°C (rounded to 200°C), 425°F = 218°C (rounded to 220°C), 450°F = 232°C (rounded to 230°C). Oven thermostats aren't precise enough for the unrounded figure to matter — a 2-3°C rounding difference is well within normal oven temperature drift.
The full Fahrenheit/Celsius/Gas Mark table
Gas Mark ¼ = 225°F = 110°C (very low, for slow-cooking or drying); Gas Mark ½ = 250°F = 130°C; Gas Mark 1 = 275°F = 140°C; Gas Mark 2 = 300°F = 150°C; Gas Mark 3 = 325°F = 165°C; Gas Mark 4 = 350°F = 180°C (standard baking temperature); Gas Mark 5 = 375°F = 190°C; Gas Mark 6 = 400°F = 200°C; Gas Mark 7 = 425°F = 220°C; Gas Mark 8 = 450°F = 230°C; Gas Mark 9 = 475°F = 240°C.
💡 Совет: Gas Mark 4 (350°F/180°C) is the most common 'default' baking temperature across cakes, cookies, and general baking — if a UK recipe just says 'moderate oven' with no number, Gas Mark 4 is the safe assumption.
Why Gas Mark is not a linear scale
Between Gas Mark ¼ and Gas Mark 4, each mark represents roughly a 25°F (14°C) step, but between Gas Mark 4 and Gas Mark 9, the steps become more compressed relative to Fahrenheit — the gap from Gas Mark 8 to 9 is only 25°F/10°C, similar to the lower marks, but the overall scale was designed around historical British gas oven regulator increments rather than a clean mathematical relationship to Celsius or Fahrenheit. This is why you can't reliably estimate an unlisted Gas Mark by linear interpolation — always check the actual table rather than doing mental math between two known points.
Fan/convection oven adjustment: minus 20°C or 25°F
Fan (convection) ovens circulate hot air, cooking food faster and more evenly than a conventional oven at the same set temperature — the widely used rule of thumb is to lower the temperature by 20°C (or about 25°F) when a recipe was written for a conventional oven but you're using a fan oven, or conversely raise it by that amount if a recipe was written for fan and you have conventional. So a recipe calling for 180°C (350°F) conventional becomes about 160°C (325°F) in a fan oven at the same bake time, or you can keep the temperature and reduce bake time by roughly 10-15% instead — either approach works, but don't do both simultaneously.
💡 Совет: UK recipes often print both temperatures already, e.g. '180°C (160°C fan)' — always check for a fan-specific number before applying the -20°C rule yourself, since the recipe writer may have already done it.
Recognizing which oven type a recipe assumes
US recipes overwhelmingly assume a conventional (non-fan) oven setting unless they specifically say 'convection,' since most US home ovens default to conventional bake. UK and European recipes are more likely to specify both temperatures or default to fan, since fan ovens are more common there. When a recipe's oven-type assumption isn't stated, check for contextual clues: a single unadorned Celsius number close to a round Fahrenheit conversion (180°C ≈ 350°F) suggests a conventional-oven US-style recipe converted directly, while two temperatures listed together signals a UK fan/conventional pairing.
Altitude adjustment: a brief note
At elevations above roughly 3,000 feet (900m), lower air pressure causes leavened baked goods to rise faster and moisture to evaporate quicker, so many high-altitude bakers increase oven temperature by 15-25°F (roughly 10-15°C) and reduce bake time slightly to set the structure before the rise over-extends, alongside separately reducing leavening agents (baking powder/soda) by 15-25% and increasing liquid slightly. This is a secondary adjustment on top of any Fahrenheit/Celsius/Gas Mark conversion, relevant mainly if you're baking above 3,000 feet — sea-level and moderate-elevation cooks can ignore it entirely.
Часто задаваемые вопросы
What is 350°F in Celsius?
350°F converts to 176.7°C, rounded to 180°C for baking purposes — this is also Gas Mark 4, the most common 'standard' baking oven temperature used across cakes, cookies, and general baking.
What is Gas Mark 4 in Fahrenheit and Celsius?
Gas Mark 4 is 350°F or 180°C, the standard moderate baking temperature. If a UK recipe just says 'moderate oven' without a number, Gas Mark 4 is the safe default assumption.
Is Gas Mark the same scale as Celsius?
No, Gas Mark is a separate, non-linear British scale that roughly tracks Celsius in the lower range but doesn't scale mathematically — you can't reliably estimate an unlisted Gas Mark number by interpolating between two known Celsius points. Always check the full conversion table rather than doing the math yourself.
Do I need to adjust the temperature for a fan/convection oven?
Yes — lower the temperature by about 20°C (25°F) if a recipe was written for a conventional oven and you're using a fan oven, since fan ovens circulate air and cook faster and more evenly at the same set temperature. Many UK recipes already print both temperatures, so check before adjusting yourself.
How do I convert Celsius to Fahrenheit?
Multiply Celsius by 9/5 (1.8) and add 32: °F = (°C × 1.8) + 32. For example, 180°C × 1.8 = 324, plus 32 = 356°F, which rounds to the commonly used 350°F baking temperature.
Fahrenheit-to-Celsius is simple arithmetic, but Gas Mark requires the actual lookup table since it isn't linear, and neither conversion accounts for fan vs. conventional ovens, which shifts effective cooking temperature by roughly 20°C on its own. Check both the temperature scale and the oven type a recipe assumes before you preheat — getting the number right but the oven-type adjustment wrong is just as likely to cause overbaking as an outright unit conversion error.
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