How oven temperatures convert
To turn Fahrenheit into Celsius, subtract 32 and multiply by 5/9. To go the other way, multiply by 9/5 and add 32. Recipes usually round to the nearest 5 or 10 degrees, so 350 °F becomes 180 °C rather than 177 °C.
Fan ovens
A fan (convection) oven moves hot air around the food, so it cooks faster. Lower the temperature by about 20 °C (25 °F) from a conventional recipe, or keep the temperature and check the food earlier.
Gas marks
Gas marks are used on older British gas ovens. Gas mark 4 is a moderate oven of about 180 °C or 350 °F. Each step up adds roughly 14 °C (25 °F).