Oven Temperature Converter
Type a temperature in Fahrenheit or Celsius, or pick a Gas Mark — the other two update instantly, along with the fan/convection oven adjustment.
Turn this on if your recipe already gives a fan-oven temperature — off means a conventional (static) oven.
Type a temperature, or pick a Gas Mark above, to see the full conversion.
Everything is calculated in your browser — nothing is sent to a server.
Gas Mark numbers are a stepped scale, not a straight-line formula — treat matches as close reference points, not exact equivalents.
Full Gas Mark conversion chart
| Gas Mark | °C (conventional) | °F | Fan / convection °C | Description |
|---|
Why oven temperatures need three different scales
A recipe written in the United States gives Fahrenheit. One written in most of the rest of the world gives Celsius. A recipe from a British cookbook — or an older oven with a dial instead of a digital display — gives a Gas Mark instead of either. None of these are wrong; they are just different eras and regions of kitchen equipment. This converter turns any one of the three into the other two instantly, and adds the one adjustment recipes rarely spell out clearly: what to do if your oven has a fan.
The Fahrenheit-Celsius formula
- Celsius to Fahrenheit: F = C × 9/5 + 32
- Fahrenheit to Celsius: C = (F − 32) × 5/9
That part is exact math. Gas Mark is different: it is a stepped, historical scale with only twelve defined points, so this tool matches your number to the nearest one rather than computing a Gas Mark with a formula.
Fan / convection ovens: the -20°C rule
A fan (convection) oven circulates hot air with a built-in fan, which cooks food faster and more evenly than a conventional (static) oven at the same dial setting. Because of that, most recipe books and oven manufacturers recommend lowering the temperature by about 20°C (roughly 25-30°F) when using a fan oven, or lowering the time instead if you keep the same temperature. This tool applies the -20°C convention once you switch the toggle to fan/convection, and always shows the other oven type's equivalent number alongside your result so you can convert a recipe either direction.
The 20°C figure is a widely used rule of thumb, not a physical law — some ovens run hotter or cooler than their dial suggests, and manufacturers occasionally suggest slightly different offsets. If a specific bake is sensitive (delicate pastry, soufflés), it is worth checking your oven's manual or doing a first test bake with an oven thermometer.
Full Gas Mark, Celsius, and Fahrenheit reference chart
| Gas Mark | °C (conventional) | °F | Fan/convection °C | Description |
|---|---|---|---|---|
| 1/4 | 110 | 225 | 90 | Very low |
| 1/2 | 120 | 250 | 100 | Very low |
| 1 | 140 | 275 | 120 | Low |
| 2 | 150 | 300 | 130 | Low |
| 3 | 160 | 325 | 140 | Warm |
| 4 | 180 | 350 | 160 | Moderate |
| 5 | 190 | 375 | 170 | Moderately hot |
| 6 | 200 | 400 | 180 | Fairly hot |
| 7 | 220 | 425 | 200 | Hot |
| 8 | 230 | 450 | 210 | Hot |
| 9 | 240 | 475 | 220 | Very hot |
| 10 | 260 | 500 | 240 | Very hot |
Common mistakes
- Treating Gas Mark as exact math: it's a lookup table of twelve standardized points, not a linear conversion — a Celsius value between two marks doesn't have its own "true" Gas Mark, only a nearest one.
- Forgetting the fan adjustment: following a conventional-oven recipe at full temperature in a fan oven commonly over-browns the outside before the inside finishes.
- Assuming every oven is calibrated correctly: home ovens can run 10-20°C off their dial reading; an oven thermometer settles the question for temperature-sensitive bakes.
Every conversion on this page runs locally in your browser; nothing you type is sent anywhere.
Sources & further reading
Frequently asked questions
What is Gas Mark, and how does it relate to Celsius and Fahrenheit?
Gas Mark is the numbering system British gas ovens have used since the 1950s, running from a very cool 1/4 up to a very hot 10. It isn't a straight-line formula like the Celsius-to-Fahrenheit conversion — each mark corresponds to a standardized temperature band that manufacturers agreed on, so the scale is a lookup table rather than math. Gas Mark 4, the classic "moderate" oven for cakes and most everyday baking, is 180°C or 350°F. This converter matches any Celsius or Fahrenheit value you type to the nearest Gas Mark automatically.
What is 350°F in Celsius, and what Gas Mark is that?
350°F converts exactly to about 176.7°C, which nearly every recipe and oven dial rounds to 180°C — Gas Mark 4, described as a moderate oven and the most common setting for cakes, biscuits, and casseroles. Type 350 into the Fahrenheit field above to see the exact Celsius figure alongside the matching Gas Mark and its fan-oven adjustment.
How much should I lower the temperature for a fan or convection oven?
The widely used rule of thumb is to lower a conventional (static) oven temperature by 20°C, or about 25-30°F, when switching to a fan or convection oven, because the moving air cooks food faster at the same setting. This converter applies that -20°C convention automatically once you turn on the fan/convection toggle. It's a good starting point, but ovens vary by manufacturer, so check your oven's manual or keep an eye on the first bake if precision matters.
Are Gas Mark conversions to Celsius and Fahrenheit exact?
No — Gas Mark is a stepped scale of only 12 fixed points (1/4 through 10), while Celsius and Fahrenheit are continuous. When you type a temperature that falls between two Gas Mark points, this tool shows the nearest match with an approximate (≈) mark rather than inventing a fractional Gas Mark that doesn't exist. If your number is well outside the normal oven range, the tool tells you there's no sensible Gas Mark match instead of guessing.
Is my oven temperature sent to a server?
No. This oven temperature converter runs entirely in your browser — every Fahrenheit, Celsius, and Gas Mark calculation happens on your device using plain JavaScript. Nothing you type is uploaded, stored, or tracked, and the page keeps working offline once it has loaded.