Oven Temperature Conversion: Gas Mark, Celsius, Fahrenheit, and Fan Ovens
October 29, 2026
British and Irish recipes often use gas marks, which are numbered settings on gas ovens. US recipes use Fahrenheit, and most of the world uses Celsius. The conversions between Celsius and Fahrenheit are °F = °C × 9/5 + 32 and °C = (°F − 32) × 5/9. For example, 180°C = 180 × 1.8 + 32 = 356°F, usually rounded to 350°F.
Gas marks do not follow a formula but a table: gas mark 4 is 350°F (180°C), a common baking temperature for cakes and cookies.
Skip the math and get your answer instantly:
Open the Temperature Converter →Conversion Chart
Gas mark 1/4 is 225°F (110°C), 1/2 is 250°F (120°C), 1 is 275°F (140°C), 2 is 300°F (150°C), 3 is 325°F (170°C), 4 is 350°F (180°C), 5 is 375°F (190°C), 6 is 400°F (200°C), 7 is 425°F (220°C), 8 is 450°F (230°C), and 9 is 475°F (240°C). Some charts list slightly different Celsius values, such as 160°C or 165°C for 325°F; for baking, a few degrees' difference rarely matters.
| Gas mark | Fahrenheit | Celsius | Description |
|---|---|---|---|
| 1 | 275°F | 140°C | Very cool |
| 2 | 300°F | 150°C | Cool |
| 3 | 325°F | 170°C | Moderately slow |
| 4 | 350°F | 180°C | Moderate |
| 5 | 375°F | 190°C | Moderately hot |
| 6 | 400°F | 200°C | Hot |
| 7 | 425°F | 220°C | Hot |
| 8 | 450°F | 230°C | Very hot |
| 9 | 475°F | 240°C | Very hot |
Fan (Convection) Ovens
A fan circulates hot air, cooking food faster and more evenly. The usual advice: reduce the temperature by 20°C (about 25°F) or cook for less time, around 10% to 20% less. A recipe calling for 180°C (350°F) conventional becomes 160°C (325°F) in a fan oven. Check your oven's manual; some US convection ovens convert automatically. Roasts brown more and cook faster with the fan, and delicate cakes may rise unevenly if the fan is strong.
Oven Accuracy
Many ovens run 10°F to 25°F off from the dial. An inexpensive oven thermometer placed in the center tells you the actual temperature. Preheat for at least 15 to 20 minutes, since the indicator light can go off before the walls are hot. Opening the door drops the temperature by 25°F or more. If a recipe fails repeatedly, test the oven.
Mental Math
A quick estimate for Celsius to Fahrenheit: double the Celsius value and add 30 (for 180°C: 360 + 30 = 390°F, which overshoots by 34°F, so for hot ovens, use the exact formula). For common baking temperatures, memorize the table.
Frequently Asked Questions
What is gas mark 4 in Celsius and Fahrenheit?
180°C and 350°F.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32.
How should I adjust for a fan oven?
Reduce the temperature by about 20°C (25°F) or shorten the time.
Why use an oven thermometer?
Because many ovens are inaccurate by 10°F to 25°F.
What gas mark is 400°F?
Gas mark 6.