Oven Temperature Calculator
Convert between Celsius, Fahrenheit, gas mark, and fan-oven equivalent
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What this calculator computes
The oven-temperature calculator converts between the four temperature systems used by domestic ovens around the world: degrees Celsius (UK, EU, AU), degrees Fahrenheit (US, Canada), gas marks (UK gas ovens, numbered 1–9 plus a quarter and a half mark), and fan-oven equivalents (where a convection fan redistributes heat and effectively raises the cooking temperature, requiring a 15–25°C downward adjustment for the same recipe). UK and US recipe books use different temperature conventions: a UK recipe specifying "180°C / Gas Mark 4 / 350°F / 160°C fan" gives all four equivalents, but recipes from one tradition often quote only their native units, leaving the cook to convert. The Celsius-to-Fahrenheit conversion is F = C × 9/5 + 32, with both scales calibrated such that water freezes at 0°C / 32°F and boils at 100°C / 212°F at sea level. Gas marks correspond to discrete temperature steps: 1/4 = 110°C/225°F, 1/2 = 130°C/250°F, 1 = 140°C/275°F, 2 = 150°C/300°F, 3 = 165°C/325°F, 4 = 180°C/350°F, 5 = 190°C/375°F, 6 = 200°C/400°F, 7 = 220°C/425°F, 8 = 230°C/450°F, 9 = 240°C/475°F. Fan-oven equivalents are typically 20°C lower than conventional-oven temperatures because the moving air transfers heat more efficiently to the food surface; the British convention is to subtract 20°C, the European is to subtract 25°C, and most modern fan ovens have an "automatic" setting that applies the offset internally so the dial reads conventional temperatures. The calculator handles all four directions and shows the equivalent in every other system simultaneously.
Calculator
The formula
Formula
°F = °C × 9/5 + 32 Fan = Conventional − 20°C
Worked example
When to use this calculator
Use this calculator any time a recipe specifies a temperature in a different unit from the one your oven uses, or to compute the fan-oven adjustment when the recipe was written for a conventional oven. The most common scenarios are UK cooks following US recipes (where Fahrenheit needs converting to Celsius and Gas Mark), US cooks following UK recipes (the reverse), and any cook with a fan oven baking from a recipe written for a conventional oven (where the 20°C downward adjustment matters most for pastries and cakes that brown unevenly when over-temperatured). The calculator does not handle older "moderate / slow / hot" oven descriptions from pre-1950s cookbooks — those map roughly to gas mark 4 / gas mark 2 / gas mark 7 respectively, but the older terminology is too imprecise for reliable conversion. For convection (fan) cooking of meat, the 20°C reduction is typically applied; for delicate baking (soufflés, choux), the reduction is closer to 25°C to prevent the surface from setting too quickly. Always verify the recipe's intent if it does not specify whether the temperature is conventional or fan.
Common input mistakes
- Using a fan-oven temperature without applying the offset, or vice versa. A recipe specifying "180°C" without further qualification is conventional-oven temperature; baking at 180°C on a fan oven will overcook the food and brown it unevenly because the moving air increases effective heat delivery by 20°C-equivalent. Modern UK fan ovens often display the conventional temperature on the dial with the fan offset applied internally; older ovens show the actual fan temperature and require manual adjustment.
- Confusing the Celsius and Fahrenheit conversion formulas. C = (F − 32) × 5/9 and F = C × 9/5 + 32 are the correct conversions; the common error is to forget the 32 offset or to use the wrong fraction (5/9 vs 9/5). For a quick mental approximation, double the Celsius and add 30 (e.g. 180°C → 360 + 30 = 390°F, vs the exact 356°F) — accurate to about ±10°F, fine for oven temperatures where the dial granularity is 25°F anyway.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Use F = C × 9/5 + 32. To convert 180°C: 180 × 1.8 = 324, plus 32 = 356°F. The reverse formula is C = (F − 32) × 5/9. For oven temperatures, the most common pairs to remember are 160°C = 325°F, 180°C = 350°F, 200°C = 400°F, and 220°C = 425°F. A quick mental approximation is double-and-add-30 for Celsius to Fahrenheit, or subtract-30-and-halve for Fahrenheit to Celsius.
What is the difference between fan and conventional oven temperatures?
Fan (convection) ovens circulate hot air with a fan, distributing heat more evenly and transferring it to food more efficiently than conventional radiant heat. The same recipe in a fan oven needs a 15–25°C lower dial setting to produce equivalent cooking, with 20°C being the British convention. Most modern fan ovens have an "auto" mode that applies the offset internally so the dial reads conventional-oven temperatures; check your oven manual for which mode you are in.
What are gas marks?
Gas marks are the temperature scale used on UK gas ovens, numbered 1–9 with quarter and half marks at the low end. They correspond approximately to: 1/4 = 110°C / 225°F, 1 = 140°C / 275°F, 4 = 180°C / 350°F, 6 = 200°C / 400°F, 9 = 240°C / 475°F. The scale is roughly logarithmic at the low end (small changes between 1/4, 1/2, 1) and linear at the high end (each mark above 4 is about 10°C). UK electric ovens have moved to °C dials but recipes still quote gas marks for historical continuity.
Should I trust the oven dial?
Domestic oven thermostats are typically accurate to ±10°C of the dial setting, with older ovens often running 20°C high or low after years of use. For critical baking (sourdough, choux, meringue, soufflé) check the actual temperature with an oven thermometer placed in the centre of the rack and adjust the dial accordingly. Most ovens also have hot spots — areas 10–20°C above average — so rotating trays partway through the bake is good practice for even results.
How do "moderate", "slow", and "hot" oven descriptions translate?
Pre-1950s cookbooks used qualitative oven descriptions: "very slow" ≈ 110–140°C / Gas 1/4–1, "slow" ≈ 150°C / Gas 2, "moderate" ≈ 180°C / Gas 4, "moderately hot" ≈ 190°C / Gas 5, "hot" ≈ 220°C / Gas 7, "very hot" ≈ 240°C / Gas 9. The terminology is too imprecise for modern recipes that depend on tight temperature control, but the rough mapping helps interpret old family recipes and historical cookbooks. Modern cookbooks have universally moved to numeric temperatures.