How oven temperature converter works
Recipes move between three temperature systems: Fahrenheit in the US, Celsius almost everywhere else, and the UK's gas-mark dial on gas ovens. The °F/°C conversion is exact — °C = (°F − 32) × 5/9 — so 350°F is 176.7°C and 180°C is 356°F. Gas marks only exist in steps: mark 1 is 275°F and every whole mark adds 25°F, with the half marks ½ = 250°F and ¼ = 225°F below it.
Converting to a gas mark is a nearest-match exercise, since 176.7°C falls between the marks. This tool snaps any temperature in the baking range (roughly 225–500°F) to the closest mark and says whether the match is exact or approximate — 350°F is exactly mark 4, and 180°C (356°F) also lands on mark 4. Below 212°F or above 512°F there is no mark to snap to, so the gas field stays empty.
Fan-assisted (convection) ovens circulate hot air and effectively run hotter, so recipes get adjusted down: US convention subtracts 25°F from the conventional temperature, UK guidance subtracts 20°C. The tool computes the fan setting in the same unit family as your input — a 350°F conventional recipe becomes 325°F fan; a 180°C recipe becomes 160°C fan.