Why use this calculator
Three scales are still in daily use and most ovens show only one of them. American recipes are written in Fahrenheit, Australian, New Zealand and European recipes in Celsius, and British gas ovens in gas marks that correspond to neither in an obvious way. On top of that sits the fan question, which catches more cooks than the scales do: a fan oven circulates hot air and browns and dries food faster, so the same dish needs a setting about 20 degrees Celsius lower than a conventional oven.
A recipe almost never says which oven it assumed. This converter gives all three scales at once, the fan setting alongside the conventional one, and the old cookbook wording such as moderate or very hot, so a temperature written in any convention can be set on any oven.
How to use it
- Type the number printed in the recipe into the first box, whether that is 350, 180 or a gas mark such as 4.
- Choose the scale the recipe used in the second field: Fahrenheit for American sources, Celsius for Australian, New Zealand, British and European ones, and gas mark for British gas oven recipes.
- Then say whether that temperature was written for a conventional oven or a fan-forced one, because the conversion between the two is the part cooks most often skip.
- If the recipe gives no hint, assume conventional, which is the default in published recipe writing.
- Read the conventional and fan rows together and set whichever one matches the oven you actually have.
What each result means
- Conventional oven (C)
- What to set a standard oven with no fan running, in Celsius, plus the rounded number recipes normally print.
- Conventional oven (F)
- The same conventional setting in Fahrenheit, for American ovens and American recipes.
- Gas mark
- The nearest gas mark on a British gas oven dial, with the Celsius and Fahrenheit figures that mark is sold as.
- Fan-forced oven (C)
- What to set if your oven runs a fan, about 20 degrees lower, rounded to the nearest mark on the dial.
- Fan-forced oven (F)
- The fan setting in Fahrenheit, shown next to the American rule of thumb of cutting 25 degrees.
- Oven description
- The wording older recipes use instead of a number, from very slow through moderate to very hot.
The formula
Between the degree scales
C = (F - 32) x 5 / 9
F = C x 9 / 5 + 32
- C
- degrees Celsius
- F
- degrees Fahrenheit
Gas marks are not a formula but a lookup: gas mark 1 is 140 C and 275 F, and each whole mark above it adds 25 F, with the quarter and half marks below covering 225 F and 250 F. The fan setting is conventional Celsius minus 20, the offset published by oven makers, and the American convection rule of thumb subtracts 25 Fahrenheit instead.
How this number is used in practice
The fan is the conversion that ruins the most food. Almost every oven sold today has a fan setting, and many people leave it on permanently without adjusting the dial. A cake baked at 180 C with the fan running is effectively baking at about 200 C, so the outside sets and browns before the middle has risen, giving a domed, cracked top and a sunken centre.
Biscuits go dark at the edges, roast vegetables scorch, and a slow braise dries at the surface. The fix is one step: if the recipe says 180 C and your oven has a fan, set 160 C.
Oven dials are also less accurate than cooks assume. Independent testing regularly finds domestic ovens running 10 to 20 degrees Celsius away from the number on the dial, with the gap varying across the cavity and changing as the element ages. A cheap oven thermometer on the middle shelf shows what the oven is really doing and is the only way to know whether your 180 C is anyone else's.
If your baking is always slightly under or over at the recipe time, the oven rather than the recipe is usually the reason.
Worked examples
An American recipe at 350 F, conventional oven
177 C, gas mark 4, and 157 C in a fan oven
A British recipe at gas mark 6
200 C and 392 F, described as moderately hot
A recipe written for a fan oven at 160 C
180 C conventional, 356 F, gas mark 4
When people use it
- Setting an American recipe written in Fahrenheit on a Celsius oven
- Following a British recipe that gives only a gas mark
- Adjusting a conventional recipe for a fan-forced or convection oven
- Reading an old cookbook that says moderate or hot instead of a number
- Checking whether your oven dial matches what the oven is really doing
Tips
- If the recipe says conventional and your oven has a fan, drop 20 degrees Celsius or 25 Fahrenheit and check ten minutes early.
- Buy an oven thermometer. Domestic ovens commonly run 10 to 20 degrees away from the dial and the error is invisible without one.
- Preheat for at least 15 minutes after the light goes out. The light marks air temperature, not the heat stored in the oven walls.
- Gas mark 4 at 180 C is the workhorse setting for cakes and most baking, and gas mark 6 at 200 C is the roasting and pastry setting.
- Fan ovens cook more evenly across shelves, so they suit batch baking. Conventional heat suits rich cakes and anything that must not dry.
- Opening the door drops the temperature sharply. Use the window and the light rather than checking by hand during a rise.
What it assumes, and where it stops being accurate
- The fan adjustment of 20 degrees Celsius is the general figure published by oven makers. Individual ovens vary and some models adjust themselves.
- Gas mark equivalents follow the standard British table, where the Celsius column is the setting printed on dials rather than an exact arithmetic conversion.
- The oven is correctly calibrated and preheated. A dial reading is not a measurement of the air inside the cavity.
- Temperatures are for domestic ovens. Commercial decks, steam ovens and air fryers behave differently at the same number.
- Gas ovens have no fan, so the fan rows do not apply when a gas mark is entered.
Terms used on this page
- Gas mark
- The numbered scale on British gas ovens, where mark 1 is 140 C and each whole mark adds 25 Fahrenheit.
- Fan-forced oven
- An oven with a fan circulating the hot air, reaching the same result about 20 degrees Celsius lower.
- Convection oven
- The American name for a fan-forced oven, with the rule of thumb of cutting 25 degrees Fahrenheit.
- Moderate oven
- Older recipe wording for about 180 C, 350 F or gas mark 4.
- Calibration
- How closely the oven dial matches the real air temperature inside the cavity.
Questions people ask
- What is 350 F in Celsius?
- Exactly 176.7 C, which every recipe and oven dial rounds to 180 C. That setting is gas mark 4 and is the standard temperature for most cakes and biscuits. In a fan-forced oven you would set about 160 C instead, since a fan reaches the same result roughly 20 degrees lower.
- How do gas marks convert to Celsius?
- Gas mark 1 is 140 C, 2 is 150 C, 3 is 170 C, 4 is 180 C, 5 is 190 C, 6 is 200 C, 7 is 220 C, 8 is 230 C and 9 is 240 C. Below those, gas mark one half is 120 C and one quarter is 110 C, used for meringues and very slow cooking.
- Should I lower the temperature for a fan oven?
- Yes. Reduce the setting by about 20 degrees Celsius, or 25 Fahrenheit in American recipes, unless the recipe states it was written for a fan oven. Moving air transfers heat much faster, so the same dial number cooks considerably harder, browning and drying the surface before the centre is done.
- What does a moderate oven mean?
- Moderate is about 180 C, 350 F or gas mark 4, the setting used for most cakes. Older books also use slow at around 150 C, moderately slow at 160 C, moderately hot at 190 to 200 C, hot at 220 C and very hot at 240 C. This calculator prints the matching description for any temperature entered.
- Why does my oven not match the recipe?
- Domestic ovens are commonly 10 to 20 degrees Celsius away from the dial setting, and the error changes across the cavity and with the age of the element. Recipes are written for a correct oven. An inexpensive oven thermometer on the middle shelf shows the real figure and lets you correct the dial once for everything you cook.
- Do I need to change the cooking time as well as the temperature?
- If you convert the temperature correctly the time should be close, but a fan oven usually finishes a little sooner even at the reduced setting. Start checking at about eighty per cent of the stated time. Judge by colour, a skewer or an internal temperature rather than by the clock alone.
Use this with
Oven Temperature Converter answers one part of the question. These pick up where it stops: Roasting Time Calculator, Temperature Converter, Cup Converter and Recipe Scaler.
Where these figures come from
This calculation is jurisdiction-neutral arithmetic. No country-specific rules are applied.
- NIST Special Publication 811, SI units guide. Metric unit symbols and conversion factors
- UK Food Standards Agency. British cooking and food safety guidance, including oven use
- Food Standards Australia New Zealand. Australian and New Zealand metric measures and food safety guidance
Oven Temperature Converter produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.