Show the formula and working
This free gas mark converter turns any gas mark from 1/4 to 10 into Celsius, Fahrenheit and fan oven settings, and turns a temperature back into the nearest gas mark, for cooks in the UK and Ireland using older British recipes or a gas cooker. Choose a direction and it shows the answer with the working.
Quick answer: A gas mark converter uses the British scale where gas mark 1 is 275 °F and each mark adds 25 °F. Gas mark 4 is 350 °F or 180 °C (160 °C fan), gas mark 6 is 400 °F or 200 °C (180 °C fan), and gas mark 7 is 425 °F or 220 °C (200 °C fan).
What Is a Gas Mark Converter?
A gas mark converter translates the numbered settings on a British gas oven into degrees Celsius or Fahrenheit, and back again. The gas mark scale runs from gas mark 1/4 at 225 °F up to gas mark 10 at 500 °F.
The formula in plain words: from gas mark 1 upwards, the Fahrenheit temperature is 250 plus 25 times the gas mark. Gas mark 4 is therefore 250 + 100 = 350 °F. To get Celsius, subtract 32 from the Fahrenheit figure, multiply by 5 and divide by 9. Recipes then round the result, so the exact 176.7 °C for gas mark 4 is printed as 180 °C. Below gas mark 1 the scale uses quarter and half steps: gas mark 1/2 is 250 °F and gas mark 1/4 is 225 °F.
How Do You Use the Gas Mark Converter?
- Pick a Direction: “Gas mark to °C and °F”, “°C to gas mark” or “°F to gas mark”.
- To convert a gas mark, choose it from the Gas mark list.
- To find a gas mark, type the recipe figure into Oven temperature (°C or °F).
- Tick This temperature is a fan oven setting if the recipe temperature is for a fan oven, so the tool adds the reduction back before matching a gas mark.
- Keep Fan oven reduction at 20 °C unless your oven manual says otherwise.
- Read the result and open “Show the formula and working” to see the exact position on the scale and every step.
What Temperature Is Gas Mark 4?
Gas mark 4 is 350 °F, which recipes give as 180 °C, or about 160 °C in a fan oven. The exact conversion is 176.7 °C, but the 180 °C figure is what UK cookbooks and packaging print. Gas mark 4 is described as a moderate oven and suits most cakes and bakes.
What Gas Mark Is 200 °C?
200 °C is gas mark 6, which is 400 °F on the gas mark scale. If your recipe says 200 °C fan, the conventional equivalent is about 220 °C, which is gas mark 7. That difference is why the tool has a fan oven tick box: gas ovens match conventional temperatures, not fan ones.
Why Do Gas Marks Not Match Celsius Exactly?
Gas marks do not match Celsius exactly because the scale was built in Fahrenheit, with each mark 25 °F apart, which is about 13.9 °C. Converted exactly, the marks land on awkward numbers such as 162.8 °C and 204.4 °C, so recipes round them to the nearest 10 °C. This is also why gas mark 3 is printed as 170 °C rather than 160 °C. When you enter a temperature, the tool matches it to the nearest printed recipe value and also shows the exact position on the scale, for example 4.2 for 180 °C.
What Should You Do If a Gas Oven Smells of Gas?
If you smell gas, open doors and windows, turn off the supply at the meter control valve if you know where it is, and call the Gas Emergency Freephone number on 0800 111 999. That is the advice in the HSE domestic gas safety FAQs, which also state that anyone paid to work on gas appliances in a home must be a Gas Safe registered engineer. Never try to repair a gas oven or its burners yourself. To see what your cooker and heating cost to run, try the gas bill calculator.
Gas Mark Conversion Chart
| Gas mark | °F | Exact °C | Recipe °C | Fan °C |
|---|---|---|---|---|
| 1/4 | 225 | 107.2 | 110 | 90 |
| 1/2 | 250 | 121.1 | 120 | 100 |
| 1 | 275 | 135.0 | 140 | 120 |
| 2 | 300 | 148.9 | 150 | 130 |
| 3 | 325 | 162.8 | 170 | 150 |
| 4 | 350 | 176.7 | 180 | 160 |
| 5 | 375 | 190.6 | 190 | 170 |
| 6 | 400 | 204.4 | 200 | 180 |
| 7 | 425 | 218.3 | 220 | 200 |
| 8 | 450 | 232.2 | 230 | 210 |
| 9 | 475 | 246.1 | 240 | 220 |
| 10 | 500 | 260.0 | 260 | 240 |
Recipe °C values follow the standard gas mark table. Fan values assume a 20 °C reduction from the recipe °C.
Worked Example: A Family Recipe in an Electric Fan Oven
Example: an old handwritten family scone recipe says “gas mark 6”, but the new kitchen has an electric fan oven. Leave Direction on “Gas mark to °C and °F”, pick “Gas mark 6” from the Gas mark list and keep Fan oven reduction at 20 °C.
The tool shows gas mark 6 as 400 °F, an exact 204.4 °C that recipes print as 200 °C. Taking 20 °C off for the fan gives 180 °C, so the oven is set to 180 °C fan.
Gas Mark Converter FAQs
What is gas mark 5 in Celsius?
Gas mark 5 is 190 °C in a conventional oven, from an exact 190.6 °C, and about 170 °C in a fan oven. In Fahrenheit it is 375 °F. It is described as moderately hot on the gas mark scale.
What gas mark is 180 °C fan?
180 °C fan is about 200 °C conventional, which is gas mark 6. Always add the fan reduction back before choosing a gas mark, because the gas mark scale matches conventional ovens. Tick the fan box in the tool and it does this for you.
What gas mark is 350 °F?
350 °F is exactly gas mark 4, because the scale puts gas mark 1 at 275 °F and adds 25 °F per mark. In Celsius, 350 °F is 176.7 °C, which recipes round to 180 °C. In a fan oven, use about 160 °C.
What is the hottest gas mark?
Gas mark 10 is the top of the standard scale at 500 °F, or 260 °C. Check your cooker’s manual for its own maximum. Temperatures above 260 °C have no gas mark, so the tool shows them as above gas mark 10.
What is gas mark 1/4?
Gas mark 1/4 is the lowest setting on the scale, at 225 °F or about 110 °C, and around 90 °C in a fan oven. It is described as a very cool oven. Gas mark 1/2 is 250 °F or about 120 °C.
Is there a simple formula for gas mark to Celsius?
Yes, for gas mark 1 and above, multiply the gas mark by 14 and add 121 for an approximate Celsius figure. Gas mark 4 gives 4 x 14 + 121 = 177 °C. The exact route is Fahrenheit first: 250 plus 25 per mark, then convert.
Browse more tools for running costs and repairs on our energy bill calculators page.
Checked October 2026. Sources: Wikipedia: Gas mark, Wikipedia: Convection oven, HSE: Domestic gas safety FAQs.