Oven Temperature Conversions: Celsius, Fahrenheit and Gas Mark

Half the recipes in my kitchen were written for someone else’s oven. American books give Fahrenheit, older British books give gas marks, and modern recipes give Celsius but rarely say whether they mean a fan oven or a conventional one. Getting this wrong is why a cake that “should take 25 minutes” is raw in the middle or burnt at the edges. Here is the full conversion table, the fan-oven rule, and an honest note about why none of it is as precise as the numbers suggest.

The conversion table

These are the standard equivalents. The Celsius figures are for a conventional (non-fan) oven, which is what gas marks and almost all Fahrenheit recipes assume.

You will notice the °C and °F columns do not convert exactly. 350°F is really 177°C, not 180°C. Recipe temperatures are rounded to friendly numbers in whichever scale the writer used, and that is fine, because domestic ovens are nowhere near accurate enough for 3°C to matter. Mine overshoots by about 10°C when it first beeps and settles down over the next quarter of an hour.

If you would rather type a number than scan a table, the oven temperature converter does Celsius, Fahrenheit, gas mark and the fan adjustment in one go. The gas mark and oven temperature conversion calculator does the same in both directions and reprints this full table underneath.

Fahrenheit to Celsius, the exact list

Every common American recipe temperature, converted exactly and then rounded to the setting you would actually use. Set the rounded figure; the difference is smaller than your oven’s own error.

One trap worth naming: an American recipe that says something like “cook until it reaches 165°F” is giving an internal food temperature (74°C for poultry), not an oven setting. Those live on a probe thermometer, and I have listed them in the internal temperatures that matter.

Celsius to Fahrenheit and gas mark, the exact list

The same thing in the other direction, for cooking from a British or European recipe in a Fahrenheit oven. The °C column is the conventional setting; the fan column is the same heat with the standard 20°C reduction.

If your recipe gives a fan temperature and you need Fahrenheit, add the 20°C back first and read the conventional row: 160°C fan is 180°C conventional, so 356°F. 180°C fan is 200°C conventional, so 392°F.

Fan ovens: drop about 20°C

A fan (convection) oven moves hot air around, which transfers heat to the food faster than still air at the same temperature. The practical rule is simple: set a fan oven about 20°C lower than the conventional temperature in the recipe. So a recipe saying 200°C conventional means about 180°C fan. In Fahrenheit the usual advice is to drop 25°F.

Some points worth knowing:

• If a modern recipe just says “180°C” with no other information, it usually means fan in current UK books and conventional in older ones and most American ones. Annoying, but true. When in doubt, use the lower interpretation and check the food early.
• Fan ovens also cook a little faster and more evenly, so start checking a few minutes before the stated time.
• Some ovens have a “fan assisted” setting with a lower fan speed. Treat it as fan and drop the 20°C anyway; you can always give the dish longer.
• Gas ovens have no fan and no conversion to worry about, but they are hotter at the top than the bottom, so shelf position does more work than the dial.

Why recipes disagree

Two recipes for the same cake can name temperatures 20°C apart and both be right, because the writers tested them in different ovens. Domestic ovens routinely run 10 to 20°C away from the number on the dial, they cycle above and below the set point rather than holding it, and the temperature varies between shelves. Recipe writers compensate for their own oven without knowing it.

A cheap oven thermometer (a few pounds, sits on the shelf) tells you what your oven actually does. If yours runs hot, you will suddenly understand a decade of scorched biscuit bottoms. I still think the thermometer is less important than simply learning your own oven’s personality and checking food early, but it settles arguments quickly.

The other big source of disagreement is the fan question above. An American recipe at 350°F, a 1970s British recipe at gas mark 4 and a modern British recipe at 160°C fan are all describing the same oven. They just assume different equipment.

The temperatures worth memorising

You do not need the whole table in your head. Most cooking happens at a handful of settings:

• 140°C (fan 120°C, gas 1): low and slow. Meringues, slow-roast shoulders, drying things out.
• 160°C (fan 140°C, gas 3): rich fruit cakes, gentle braises, anything that needs a long time without colouring.
• 180°C (fan 160°C, gas 4): the general baking temperature. Sponges, cookies, brownies, banana bread. If a baking recipe has lost its temperature, this is the safest guess.
• 200°C (fan 180°C, gas 6): roast vegetables, chicken pieces, pies, most weeknight oven dinners.
• 220°C (fan 200°C, gas 7): crisping and browning. Roast potatoes, pizza (as hot as your oven goes, honestly), bread with a good crust, the first blast on a roast joint.

A useful pattern: below about 160°C you are cooking gently and evenly; 180°C is for baked goods that need to rise and set; 200°C and up is for browning and crisping. If you understand which of those three jobs your dish needs, you can survive any missing or foreign temperature.

Quick mental conversions

For Fahrenheit to Celsius without a phone: subtract 32, halve it, then add a tenth of that back. In practice, halving after subtracting 32 gets you close enough for oven work (350°F: 350 minus 32 is 318, half is 159, call it 160 to 180°C and you are in the right zone). Going the other way, double the Celsius and add 30 lands near enough at oven temperatures.

For gas marks, remember that gas mark 4 is 180°C and each mark up or down is roughly 10 to 15°C. Mark 1 is 140°C, mark 6 is 200°C, mark 9 is 240°C.

If you are converting cup and gram measurements from the same foreign recipe, the cooking conversions reference covers those, and it matters more than the oven temperature does. An oven 10°C out changes your timing; flour 30 per cent out changes your cake.

When precision actually matters

Mostly it does not. Roasts, casseroles, traybakes and vegetables tolerate a 20°C error with grace. The cases where you should be careful:

• Meringues and macarons: too hot and they colour and crack. Err low.
• Choux pastry and Yorkshire puddings: need genuine high heat at the start to puff. Err high and do not open the door.
• Rich fruit cakes: hours in the oven amplify small errors. Use a thermometer or check often.
• Anything with a doneness temperature of its own, like a roast joint, where the oven setting matters less than the internal temperature. A probe thermometer solves that entirely, and I have written up the internal temperatures that matter separately.

Takeaway: gas mark 4 = 180°C = 350°F, drop 20°C for fan, and trust an early check of the food over any number on the dial.