Oven Temperature Conversion Chart: Fahrenheit, Celsius, Gas Mark & Fan Oven

Fahrenheit and Celsius convert with one exact formula: °F = °C × 9/5 + 32, and reversed, °C = (°F − 32) × 5/9. Gas mark and fan (convection) oven settings are a different kind of conversion: they are approximate, appliance-dependent conventions that cooks and oven manufacturers settled on for convenience, not outputs of that formula. 350°F, for example, converts by exact math to 176.7°C, yet almost every recipe and oven dial prints 180°C for that same setting, because kitchen charts round to a convenient, memorable number rather than the decimal the math produces. This chart gives the exact formula with the arithmetic shown, the rounded figures recipes actually use, the UK gas mark scale, the fan-oven adjustment rule of thumb, and worked examples for converting between all four.

If you need to convert an ingredient amount rather than an oven setting, the grams to cups conversion chart covers that side of the kitchen.

Four Systems for One Oven

An oven’s heat can be described four different ways, and only one of the four is pure math.

• Fahrenheit (°F). The scale most US recipes and ovens use. Water freezes at 32°F and boils at 212°F at sea level.
• Celsius (°C). The metric scale used almost everywhere else, including the UK alongside gas mark. Water freezes at 0°C and boils at 100°C at sea level.
• Gas mark. A numbered scale (¼, ½, 1 through 10) that British gas cookers used before they carried thermostatic dials with numbers on them. Each mark corresponds to a specific, agreed Fahrenheit and Celsius value, but the scale itself is a lookup convention, not a formula you can compute from Fahrenheit or Celsius directly.
• Fan (convection) oven. Not a temperature scale at all. It is an adjustment applied to a Fahrenheit, Celsius, or gas mark setting because a fan circulates hot air and transfers heat to food faster than a still oven at the same set temperature.

Fahrenheit and Celsius measure the same physical thing on two different scales, so a single formula moves between them exactly, every time. Gas mark and fan adjustments describe how ovens and recipes behave in practice, so they are approximate by nature and vary by appliance. Keeping that distinction in mind is the difference between an exact conversion and a reasonable starting point.

The Exact Math: Converting Fahrenheit and Celsius

The formula is fixed:

• °C to °F: °F = °C × 9/5 + 32
• °F to °C: °C = (°F − 32) × 5/9

The 5/9 and 9/5 come from the size of a degree on each scale: a Celsius degree is larger than a Fahrenheit degree, in a ratio of 9 to 5, because Celsius spans 100 degrees between freezing and boiling while Fahrenheit spans 180 degrees over the same range (212 − 32 = 180). The +32 shifts the scale, since 0°C is not 0°F.

Two full worked calculations:

350°F to Celsius. (350 − 32) × 5/9 = 318 × 5/9 = 1,590 ÷ 9 = 176.67°C.

325°F to Celsius. (325 − 32) × 5/9 = 293 × 5/9 = 1,465 ÷ 9 = 162.78°C.

Running the same formula on every common baking temperature gives exact, decimal-precision results:

Those figures are mathematically correct and will always be correct, because they follow directly from the formula. No recipe or oven dial uses them as printed, which is the point of the next section.

Practical Oven Settings: The Rounded Numbers Recipes Actually Use

Oven dials are built with round numbers: multiples of 5, 10, or 25, not decimals like 176.7. Recipe authors, cookbook editors, and appliance manufacturers settled decades ago on a standard set of rounded Celsius figures to pair with each common Fahrenheit setting, and that rounded set, not the raw math, is what actually appears in print. The National Institute of Standards and Technology (NIST) Metric Kitchen: Culinary Temperature guidance lists oven heat as ranges rather than single numbers, for example “Moderate: 180–190°C / 350–375°F” and “Moderately Hot: 190–200°C / 375–400°F,” which is itself an acknowledgment that kitchen temperature conversion is a practical approximation, not a single-point calculation.

This is also why older, handwritten recipes describe oven heat with words instead of numbers. A card that says only “a moderate oven” is using exactly the kind of descriptive range NIST’s table still uses today; see converting a family recipe with vague instructions like that for how to handle temperatures (and other measurements) that were never written down precisely in the first place.

Here is how the exact math compares with the figure that actually gets printed on charts and dials:

The gap is not constant. At 375°F the exact math (190.6°C) and the printed figure (190°C) are almost identical. At 325°F the gap is much larger: exact math gives 162.8°C, but the number on every chart is 170°C, a difference of more than 7°C (about 13°F). Both the exact and the rounded numbers are “correct” in their own context: the exact figure is the true mathematical conversion, and the rounded figure is the one a recipe, a printed chart, or an oven dial actually expects you to use.

Gas Mark, Explained

Gas mark is a British numbering system, running from ¼ and ½ up through 10, that predates the thermostatic ovens most people cook with now. According to Delia Online’s oven temperatures and conversions guide, a widely used British culinary reference, the scale steps up in roughly 25°F (about 14°C) increments per mark, and the anchor most cooks remember is gas mark 4, which equals 350°F and 180°C: a moderate oven for everyday baking. Gas mark 2 is a slow oven at 300°F/150°C, gas mark 6 is a hot oven at 400°F/200°C, and gas mark 8 is a very hot oven at 450°F/230°C. The full scale is in the chart below.

Because gas mark was built as a lookup table rather than derived from the Fahrenheit/Celsius formula, converting into or out of gas mark means matching against that table, not calculating. There is no equation that turns 218.3°C (the exact math for 425°F) into “gas mark 7.” Gas mark 7 is simply the entry the table assigns to that oven setting.

Fan and Convection Ovens: The Adjustment Isn’t Exact Math

A fan or convection oven moves hot air around the food instead of relying on it to rise and settle on its own. Moving air transfers heat to food faster than still air at the same temperature, so a dish in a fan oven set to the same number as a conventional oven will generally cook hotter and faster. Recipe writers and appliance manufacturers compensate by telling cooks to dial the fan oven down.

Two separate rules of thumb exist for this, from two different culinary traditions, and they do not describe the same number of degrees:

• UK convention: reduce the conventional-oven or gas-mark temperature by about 20°C, or drop one gas mark, when using a fan-assisted setting. Delia Online states this directly: for a fan oven, “reduce the temperature by 20 degrees centigrade, or check the manufacturer’s handbook.”
• US convention: reduce the conventional-oven temperature by about 25°F when using a convection setting. King Arthur Baking’s guidance on convection ovens recommends lowering the temperature by 25°F and checking the food about 10 minutes earlier than the recipe states.

Neither adjustment is exact, and they are not simply the same rule expressed in two units. Take a 400°F conventional setting, which the practical chart above pairs with 200°C. Apply the US rule and you get 375°F. Apply the UK rule to the Celsius figure and you get 180°C. Those two “fan-adjusted” numbers are not equivalent: 375°F converts by exact math to 190.6°C, not 180°C, an 11°C (about 19°F) gap between the two rules of thumb. That gap is the clearest proof that fan-oven guidance is a rounded, oven-dependent convention on both sides of the Atlantic, not a physical law with one correct answer. A powerful commercial-style fan may need a bigger reduction than 20°C, while a gentle domestic fan may need less; when a fan oven’s own manual gives a different figure, follow the manual over any rule of thumb printed here or anywhere else.

Full Oven Temperature Conversion Chart

This is the practical chart: the rounded numbers that recipes, oven dials, and gas cookers actually use, with the fan-oven figure calculated using the 20°C rule of thumb described above.

Use the Fahrenheit or Celsius column for a conventional (non-fan, non-convection) oven, the Gas Mark column for a UK gas cooker, and the Fan Approximation column as a starting point for a fan-assisted or convection oven, adjusting after your first bake if your particular oven runs hot or cold.

Worked Examples

1. A family recipe says 375°F; you’re baking for a UK relative with a gas oven. Exact math: (375 − 32) × 5/9 = 190.6°C. The chart rounds that to 190°C, which lines up with gas mark 5. Set the gas oven to mark 5, not mark 6, even though 190.6 is closer to 200 than a quick glance might suggest.

2. A UK recipe calls for “gas mark 6, fan 180°C,” and your oven only has a Fahrenheit dial with no fan setting. Gas mark 6 equals 200°C on the standard table. Converting 200°C with the exact formula gives 200 × 9/5 + 32 = 392°F, but the practical chart equates gas mark 6 with 400°F, so set a conventional Fahrenheit oven to 400°F. If your oven does have a convection setting and you want to use it, apply the US rule of thumb and set it about 25°F lower, around 375°F.

3. Your oven’s dial only goes up to 500°F, and a pizza recipe calls for 250°C. Exact math: 250 × 9/5 + 32 = 482°F. Round up to the nearest dial increment, 500°F if that is the closest setting available, since most home ovens cannot hold a precise 482°F reading anyway.

4. A pie-crust recipe calls for 425°F. Exact math: (425 − 32) × 5/9 = 218.3°C. The chart rounds that to 220°C, or gas mark 7. If the same oven is fan-assisted, the rule of thumb points to roughly 200°C (220°C minus 20°C).

5. A European recipe gives 220°C with no Fahrenheit listed. Exact math: 220 × 9/5 + 32 = 396 + 32 = 428°F. The practical chart rounds 220°C to 425°F (matching gas mark 7), so use 425°F on a Fahrenheit dial rather than the raw 428°F the formula produces.

6. Checking the famous 350°F/180°C pairing in both directions. Converting 350°F to Celsius gives 176.7°C. Converting 180°C back to Fahrenheit gives 180 × 9/5 + 32 = 356°F. Neither result matches the other starting number exactly. Recipes still treat 350°F and 180°C as the same setting because both are the conventional rounded figures for gas mark 4, not because the math is reversible to a whole number in both directions.

Oven Calibration: Why the Chart Is a Starting Point

Every number in this article assumes the oven reaches the temperature its dial or display claims. Many home ovens do not, by a meaningful margin. America’s Test Kitchen’s review of oven thermometers notes that “a well-calibrated oven can cycle through temperatures that are as much as 25 degrees above and below that target temperature,” and an oven that is out of calibration can be off by considerably more than that in one consistent direction, running hot or cold on every bake.

A correct conversion from Fahrenheit to Celsius, gas mark, or a fan setting only tells you what number to set. It cannot tell you what temperature your specific oven actually reaches at that setting. The only way to know is to put an independent oven thermometer on the middle rack, let the oven preheat and settle, and compare its reading with the dial. If the two disagree by more than about 15 to 20 degrees Fahrenheit (roughly 8 to 11°C), adjust the dial setting up or down to compensate on every future bake, rather than adjusting the recipe’s temperature.

Common Mistakes When Converting Oven Temperatures

1. Treating the fan-oven adjustment as exact. The 20°C/25°F/one-gas-mark rule of thumb is a starting point, not a formula, and it varies by oven power and manufacturer.
2. Running the exact formula and using the decimal. Setting an oven to 176.7°C instead of the standard 180°C will not ruin a recipe, but it is not what the recipe author tested with, and most dials cannot hold a fraction of a degree regardless.
3. Converting a printed Celsius figure with the formula instead of matching it to the chart. 200°C is not simply “converted” into gas mark 6, it is looked up on the gas mark table, since gas mark is not derived from the Fahrenheit/Celsius formula.
4. Ignoring where the recipe was written. A US-published recipe uses Fahrenheit conventions; a UK-published one may mix gas mark, Celsius, and fan Celsius in the same line. Match the conversion to the source, the same way measuring by the wrong cup standard causes errors in ingredient amounts.
5. Assuming the dial temperature is the oven’s real temperature. See the calibration section above: a correct conversion still needs a thermometer check.

Quick Reference

• Exact formula: °F = °C × 9/5 + 32, and °C = (°F − 32) × 5/9.
• Practical rounding: recipes and dials use standard rounded figures (300°F≈150°C, 350°F≈180°C, 400°F≈200°C, 425°F≈220°C), not the raw decimal the formula produces.
• Gas mark: a lookup table, not a formula; gas mark 4 (350°F/180°C) is the anchor most cooks remember.
• Fan/convection adjustment: about 20°C, 25°F, or one gas mark lower than the conventional setting, as an appliance-dependent starting point, not an exact conversion.
• Calibration: a correct conversion still assumes the oven reaches its set temperature; an oven thermometer is the only way to confirm that.

For other printable kitchen references, browse the conversion charts on this site, and remember that oven temperature and ingredient measurement are separate sources of error: getting the degrees right matters as much as weighing or measuring the ingredients themselves correctly. If you are adapting a recipe further, switching to a different baking pan and scaling the ingredient list up or down both change the bake time independently of the oven temperature covered here.