"Preheat to 180 °C / 350 °F / Gas 4" — three numbers for the same oven setting. If you have ever wondered how they relate, or why your fan oven burns everything 10 degrees hotter than the recipe expects, this guide is for you. By the end you will be able to convert between all four common scales in your head, and you will know exactly what to do when the oven and the recipe disagree.
The four scales, briefly
Celsius (°C) is used across most of the world and by professional bakers. Fahrenheit (°F) is standard in the United States. Gas Mark is a numbered scale used on British gas ovens, where Gas 4 equals 180 °C / 350 °F and each mark up or down changes the temperature by about 14 °C. Fan / convection ovens are not a separate scale but a different cooking method that runs hotter in practice.
The conversions you will actually use
The exact formula is °F = (°C × 9/5) + 32, and °C = (°F − 32) × 5/9. But baking rarely needs decimals, so bakers use a rounded ladder:
| Celsius | Fahrenheit | Gas Mark | Common use |
|---|---|---|---|
| 110 °C | 225 °F | ¼ | slow, low: dried fruit, meringues |
| 120 °C | 250 °F | ½ | very slow cooking |
| 140 °C | 275 °F | 1 | slow roasting |
| 150 °C | 300 °F | 2 | slow cakes, cheesecakes |
| 160 °C | 325 °F | 3 | sponge cakes, custards |
| 180 °C | 350 °F | 4 | most cakes, cookies, breads |
| 190 °C | 375 °F | 5 | roast vegetables, puff pastry |
| 200 °C | 400 °F | 6 | roasting, quick breads |
| 220 °C | 425 °F | 7 | hot roasting, pizza |
| 230 °C | 450 °F | 8 | very hot: pizza, puff pastry |
| 240 °C | 475 °F | 9 | searing hot |
| 260 °C | 500 °F | 10 | wood-fired pizza style |
Our oven temperature converter handles all four including fan settings, instantly and without an internet connection.
Fan ovens: the −20 °C rule
A fan oven circulates air constantly, so it transfers heat to food faster than a still oven. The standard advice: if a recipe was written for a conventional oven, set your fan oven about 20 °C (about 35–40 °F) lower, and check 5–10 minutes early. Our converter applies this automatically when you switch to Fan mode.
The reverse also matters. If you are converting a fan-oven recipe to a conventional oven, add roughly 20 °C back. And remember: "fan forced", "convection" and "turbo" all describe the same concept with different brand names.
Gas Mark explained
British gas ovens use a dial from ¼ to 10. The relationship is roughly: °C ≈ 140 + (Gas Mark × 14). Gas 1 ≈ 140 °C, Gas 4 ≈ 180 °C, Gas 6 ≈ 200 °C, Gas 9 ≈ 240 °C. Old recipes from the UK, Australia and New Zealand often give only the gas mark, which is why conversion tables stay so popular. Our converter includes all twelve marks, including the awkward half-marks used for gentle cooking.
Ovens lie — calibrate yours
The number you dial and the temperature inside your oven are often different. Studies of home ovens routinely find them running 10–25 °C off the dial. The practical consequences: cookies that spread too much or too little, cakes that dome or sink, bread that browns before it rises.
To calibrate, place an oven thermometer on the middle rack, preheat for 30 minutes, and read it. If your oven reads 195 °C when the dial says 180 °C, mentally convert recipes to "dial = target + 15 °C" until you buy a new oven. Oven thermometers cost a few dollars and are the best baking purchase most people never make.
Hot spots and rack position
Even a calibrated oven is hotter near the elements and at the back. For even baking, rotate pans halfway through and bake one tray at a time when possible. Convection ovens reduce hot spots because moving air equalises temperature — another reason fan modes are popular for biscuits and pastry. For delicate cakes, the middle rack and a still (non-fan) setting usually give the gentlest, most even heat.
High altitude and temperature
At altitude, water boils below 100 °C, and leavening gases expand more. Bakers at 1,500 m and above typically raise baking temperature by 10–15 °C (about 25 °F) while slightly reducing leavener and liquid. See our high-altitude baking guide for the full adjustment table.
Putting it together
Temperature conversions are the easiest part of baking — the scales are just labels for the same heat. The skill is knowing when to trust the recipe (most of the time), when to trust the thermometer (always), and when to adapt for your equipment. Bookmark the converter, buy a thermometer, and your oven will finally bake the way the dial always promised.