Oven Temperature Conversion: Celsius, Fahrenheit, and Gas Marks

Why oven conversions go wrong so often

A recipe written for 180°C will not work if you dial “180” on a Fahrenheit oven — that is barely warmer than a hot day, not a moderate bake. The reverse mistake is just as common: a US recipe that says “350°F” plugged into a Celsius dial as 350 destroys the dish and can trip an oven’s over-temperature protection. Oven conversion is one of the few unit mistakes that people make repeatedly because both scales use similar-looking three-digit numbers in the cooking range.

UK recipes add a third system: gas marks (Gas Mark 1 through 9), still printed on many British and Irish ovens and cookbooks. Gas marks are approximate bands rather than exact temperatures, which is why a careful conversion table always includes a range and why “Gas Mark 4” is usually listed as about 180°C / 350°F rather than a single precise value.

The formulas that actually matter in the kitchen

Celsius to Fahrenheit: °F = (°C × 9/5) + 32. Fahrenheit to Celsius: °C = (°F − 32) × 5/9. For ovens you almost never need more than whole degrees — round to the nearest 5°C or 25°F because most consumer ovens are not more accurate than that anyway.

Worked example: 200°C → (200 × 9/5) + 32 = 392°F, which recipes usually round to 400°F for a hot bake. Going the other way, 350°F → (350 − 32) × 5/9 = 176.7°C, which cookbooks round to 180°C. Memorizing that 180°C ≈ 350°F and 200°C ≈ 400°F covers a huge share of everyday baking.

Common baking temperatures at a glance

• 120°C / 250°F — very slow (dehydrating, some meringues, overnight “low and slow”)
• 150°C / 300°F — slow (gentle roasting, some custards)
• 160–170°C / 325°F — moderately slow (rich cakes, cheesecakes)
• 180°C / 350°F / Gas Mark 4 — moderate (most cookies, many cakes, everyday roasting)
• 190°C / 375°F / Gas Mark 5 — moderately hot (pastries, some breads)
• 200°C / 400°F / Gas Mark 6 — hot (pizza, roasted vegetables, many yeast breads)
• 220°C / 425°F / Gas Mark 7 — very hot (crusty breads, some roasting)
• 230°C+ / 450°F+ / Gas Mark 8–9 — extremely hot (pizza stones, finishing blasts)

Fan (convection) ovens change the numbers

Many European and newer North American ovens include a fan/convection mode that circulates hot air. Manufacturers and recipe writers often recommend reducing the temperature by about 20°C (roughly 25–40°F) when using fan mode compared with conventional static heat, or shortening the time. If a European recipe says “180°C fan,” that is already adjusted — do not reduce it again on a fan oven.

If your US oven only has Fahrenheit markings and a European recipe says “180°C (fan),” convert 180°C to about 350°F and use convection if available. If you only have conventional heat, keep 350°F and expect to need a few extra minutes — watch the food, not only the timer.

Gas marks without the guesswork

Gas Mark 1 is roughly 140°C / 275°F; each mark up adds about 10–15°C until Gas Mark 9 around 240°C / 465°F. Because marks are bands, treat them as starting points: check doneness early the first time you bake a new recipe on an unfamiliar oven.

If your oven has neither Celsius nor gas marks — only Fahrenheit — convert the Celsius (or gas mark midpoint) once, write the Fahrenheit equivalent in the margin of the recipe, and reuse that note next time. One careful conversion beats three burned trays.

Food safety temperatures are not the same as oven settings

Oven dial temperatures describe the air inside the cavity. Safe internal temperatures for meat and leftovers are measured in the food with a probe thermometer (for example poultry typically to 74°C / 165°F in many food-safety guidelines). Never assume that setting the oven to a “safe” number means the center of a roast has reached a safe temperature.

When converting a food-safety chart between Celsius and Fahrenheit, use the exact formula and do not round aggressively — a few degrees matter more for pathogen kill steps than for cookie browning.

Practical checklist before you bake

• Identify which scale the recipe uses (°C, °F, or Gas Mark) before you touch the dial
• Convert once with a trusted tool, then write the equivalent on the recipe card
• Note whether the recipe assumes fan/convection
• Preheat fully — many ovens lie about when they are ready; an oven thermometer is cheap insurance
• Use the Celsius↔Fahrenheit converters on ConvertHub when you are unsure, then confirm with visual doneness