Cooking Temperature Conversions: Why Your Oven Setting Is Probably Wrong

Recipe says 350°F. Your oven dial says 350°F. The cake still comes out dry on the outside and raw in the middle. The reason is that oven dials typically run 10–25°F off the true temperature, and the conversion between Fahrenheit, Celsius, and gas marks is not as linear as most charts suggest. Getting this right is the difference between a recipe working and a recipe failing twice.

The Core Conversions

The formula is exact: °C = (°F − 32) × 5/9. But kitchen rounding introduces real error. Here are the conversions that matter most in practice:

Fahrenheit	Celsius (exact)	Common Recipe Rounding	Gas Mark	Typical Use
250°F	121°C	120°C	½	Slow drying, meringue
300°F	149°C	150°C	2	Slow roast
325°F	163°C	160°C	3	Delicate bakes
350°F	177°C	180°C	4	Cakes, cookies
375°F	191°C	190°C	5	Pastry, bread
400°F	204°C	200°C	6	Roast vegetables
425°F	218°C	220°C	7	Pizza, searing
450°F	232°C	230°C	8	High-heat roast

Note the 177°C → 180°C rounding. That 3-degree shift is a 1.7% temperature increase, which matters more than it sounds in long bakes. For accurate values in either direction, use our temperature converter.

Why the Oven Is the Real Problem

An oven set to 350°F rarely holds a steady 350°F. Typical behavior:

• Overshoot: cycles peak 15–25°F above the set point before the element cuts off
• Undershoot: dips 10–20°F below before reheating
• Calibration drift: a dial reading 350°F may produce a true 335°F or 375°F
• Rack position: the top third of an oven runs 20–30°F hotter than the middle

A $15 oven thermometer sitting on the middle rack will reveal your oven’s actual offset in one heating cycle. This is the single highest-return purchase in a kitchen.

Fan (Convection) Adjustment

Convection ovens move air and therefore cook faster. The standard adjustment is to reduce the temperature by 25°F (roughly 15°C) from a conventional recipe, or reduce the time by about 25%. A recipe calling for 375°F conventional becomes 350°F convection. Baking at the unadjusted temperature in a fan oven is a common cause of over-browned exteriors with undercooked centers.

Candy and Meat: Where Precision Is Non-Negotiable

Some conversions cannot be rounded at all:

Stage	°F	°C
Thread	230–234	110–112
Soft ball	235–240	113–116
Firm ball	244–248	118–120
Hard crack	300–310	149–154

A candy thermometer is mandatory here — a 5°F error moves you an entire stage and ruins the batch.

Frequently Asked Questions

Can I just add 180°C for every 350°F? No. The exact conversion is 176.7°C. Rounding up by 3°C compounds across a 60-minute bake.

Does altitude matter? Above 3,000 ft, water boils lower, so baked goods need temperature increases of 15–25°F. This is separate from the unit conversion.

Gas marks to Celsius? Multiply the gas mark by 14 and add 121. Gas Mark 4 → (4 × 14) + 121 = 177°C, matching the 350°F row above.

Do This First

Buy an oven thermometer, find your oven’s real offset, and convert every recipe using exact math rather than kitchen rounding. Use the temperature converter when a recipe gives you units you do not cook in, and record your oven’s true offset on a note inside the door.