Oven Temperature Converter

Three countries, three systems. The US uses Fahrenheit, Europe and most of the world use Celsius, and the UK uniquely uses Gas Mark alongside Celsius. On top of that, modern ovens come in conventional, fan, fan-assisted, and convection variants — each requiring a different temperature setting for the same recipe.

A recipe that says "bake at 350°F" means 180°C in a conventional oven, but only 160°C in a fan oven. A recipe that says "Gas Mark 6" means 200°C — but 180°C if you have a fan oven. Getting this wrong by even 20°C can mean the difference between a golden cake and a burnt one, or between a moist brownie and a dry one.

This converter handles all four systems — Fahrenheit, Celsius, Gas Mark, and Fan Oven — so you can convert any recipe to match your specific oven. Enter a temperature in any system and instantly see all the others.

Gas Mark is a temperature scale used exclusively on gas ovens in the UK and Ireland. It was introduced in 1943 by the "New World" brand (under the Regulo name) as a simple numbered dial system. Each Gas Mark number represents a 25°F (approximately 14°C) increment.

The scale starts at Gas Mark ¼ (225°F / 110°C — "very cool") and goes up to Gas Mark 10 (500°F / 260°C — "extremely hot"). Most baking and roasting happens between Gas Mark 3 and Gas Mark 7.

Key formula: Gas Mark × 25 + 250 = °F. So Gas Mark 4 = (4 × 25) + 250 = 350°F = 180°C. This formula works for whole numbers (Gas Mark 1-10). For fractions (¼ and ½), use the table above.

Modern UK ovens increasingly show both Gas Mark and °C on their dials. If your recipe only gives a Gas Mark number, this converter gives you the exact Fahrenheit, Celsius, and fan oven equivalent.

A fan oven (also called "convection" in the US) circulates hot air around the food using a fan. This means food cooks faster and more evenly because hot air reaches all surfaces simultaneously, eliminating the hot spots found in conventional ovens.

The standard rule is to reduce the temperature by 20°C (about 25°F) when using a fan oven instead of a conventional oven. So if a recipe says 200°C conventional, use 180°C fan. This is the industry-standard adjustment used by BBC Good Food, Delia Smith, and most UK recipe publishers.

In addition to reducing temperature, fan ovens typically reduce cooking time by 10-15%. This means a cake that takes 30 minutes in a conventional oven might be done in 25-27 minutes in a fan oven. Always check 5-10 minutes before the stated time.

When NOT to reduce temperature

• Bread: Some bakers prefer full conventional temperature for the initial rise (first 10 minutes), then reduce to fan temperature
• Pizza: Use the highest temperature your oven reaches — fan or not
• Meringues: Very low temps — stick with the recipe temperature
• Custards and soufflés: Gentle heat is critical — use conventional without fan if possible

Studies show that most ovens are inaccurate by 15-25°C (25-50°F) from the temperature shown on the dial. Some ovens run hot, some run cold, and many have uneven heat distribution. An oven thermometer (£5-10 / $5-10) placed on the middle rack tells you the actual temperature inside.

How to calibrate: Set your oven to 180°C (350°F), wait 20 minutes for it to stabilise, then check the thermometer. If it reads 170°C, your oven runs 10°C cold — increase the dial by 10°C for every recipe. If it reads 195°C, it runs hot — reduce by 15°C.

Even expensive ovens can be off. The thermostat cycles on and off, creating temperature swings of ±10°C. This is normal — but knowing your oven's tendencies lets you adjust and get consistent results.