Oven Temperature Converter

Three scales, one oven. Fahrenheit is used in the United States, Celsius almost everywhere else, and the UK gas mark is a legacy of gas ovens where the temperature knob is calibrated to numbered marks rather than degrees. All three describe the same physical thing — the air temperature inside the oven — so converting between them is arithmetic, not guesswork.

The Fahrenheit ↔ Celsius formula

°C = (°F − 32) × 5/9 and °F = °C × 9/5 + 32. These are exact conversions. For quick mental math: subtract 30 from the Fahrenheit reading and halve it to get an approximate Celsius reading (good to within a few degrees at oven temperatures). So 350°F ≈ (350 − 30) ÷ 2 = 160°C, close enough to the exact answer of 177°C for most practical baking. This calculator does the precise math, then rounds to the nearest 5° because ovens don't respond to smaller changes.

How gas marks fit in

UK gas marks are a step scale, not a linear temperature. Gas mark 1 is 275°F / 140°C, gas mark 9 is 475°F / 240°C, and each step in between is roughly a 25°F / 12°C increase. Below gas mark 1 there are two half-marks (¼ and ½) for very slow cooking — meringues, dehydrating, long braises. The full canonical chart appears above; this converter interpolates between marks so you can type in any temperature and get a fractional gas mark back.

Fan ovens run hotter than the number on the dial

A fan (convection) oven circulates air actively, which increases heat transfer to the food. The standard rule is that a fan oven runs about 20°C (35°F) hotter at the food surface than a conventional oven at the same setting. European recipes often quote temperatures as "180°C / 160°C fan" for exactly this reason. If your recipe was written for a conventional oven and yours is a fan oven, drop the setting by 20°C or 35°F — or set it to the same temperature and knock 20–25% off the time.

Rounding, and why 350°F is 180°C almost everywhere

The exact Celsius equivalent of 350°F is 176.67°C. Most cookbooks round to 180°C because 5° steps are what oven dials actually resolve. Similarly, 400°F is exactly 204.4°C but recipes call for 200°C — that 4-degree gap is negligible for baking. This converter rounds outputs to the nearest 5° so the result matches what you'll find in a printed cookbook.

When precise temperature really matters

For most home cooking, ±5°F is invisible. The exceptions are enriched breads (which set at specific internal temperatures), custards (which curdle if the oven is too hot), and macarons and meringues (which need low, steady heat to dry without browning). For those categories, if your recipe is written in the opposite scale from your oven, trust the converter's exact number rather than rounding aggressively — a 10°F miscalibration will show up in the finished crumb.

For everything else — roast chicken, cookies, quick breads, casseroles — round to the nearest 5° and use an oven thermometer to check that the number on the dial matches the number in the box. Domestic ovens routinely drift 25°F off the setting; the conversion is only as accurate as the oven's calibration.