How to use the oven gas mark converter
- Choose whether you are starting from a gas mark, degrees Celsius or degrees Fahrenheit.
- Type the gas mark (1/4, 1/2 or a whole number from 1 to 9), or the temperature in the scale you chose.
- Optionally open the advanced options and enter how many degrees lower a fan oven should be set.
- Read the temperature in the other scales, the nearest gas mark for a temperature and the table of every gas mark.
Formula
gas mark 1 = 275 F and each whole mark adds 25 F; marks 1/4 and 1/2 are 225 F and 250 F
Celsius = (Fahrenheit - 32) x 5 / 9
Fahrenheit = Celsius x 9 / 5 + 32
Oven dials usually print rounded Celsius values such as 180 C for gas mark 4, so the exact conversion can differ from the dial by a few degrees. Between two marks the page uses straight steps along the table.
Gas mark 4 and a 200 C recipe
Gas mark 4 is 350 F, which is exactly 176.7 C. Many oven dials show 180 C for this mark. In the other direction, 200 C is 392 F, between gas mark 5 (375 F) and gas mark 6 (400 F), and nearest to gas mark 6.
For a fan oven, lowering gas mark 4 by 20 C gives 156.7 C, shown as 157 C or 314 F, which lies between gas marks 2 and 3 and is nearest to gas mark 3. The 20 degree offset is an example you can change.
About the scale
Gas marks are a British scale for gas ovens, and recipes from the United Kingdom and some other countries still use them. The scale runs from 1/4 to 9 in this table. Each whole step is 25 F, about 14 C, which is why Celsius values on dials are rounded to the nearest 10.
Fan ovens move the air and cook faster, so recipes usually ask for a lower temperature or a shorter time. The Convection Oven Conversion Calculator adjusts both. To swap baking pans and scale a recipe, see the Baking Pan Size Converter, and for cups, grams and spoons the Cooking Measurement Converter.
Trust your own oven
Real ovens run hotter or cooler than their dials, and some have hot spots. An oven thermometer shows what yours really does. If a recipe is sensitive, such as a cake or bread, check it by color and doneness as well as the clock, and follow the instructions for your own oven.
Assumptions and limits
- The table has the marks 1/4, 1/2 and 1 to 9; temperatures outside 225 F to 475 F are rejected.
- The dial values for Celsius are the ones printed on many ovens, and they are rounded.
- The fan oven offset is subtracted from the Celsius figure and defaults to 0.
- Straight-line steps are used to place a temperature between two marks.
- The conversions do not depend on altitude, humidity or the type of oven.
Frequently asked questions
What is gas mark 4 in Celsius?
Exactly 176.7 C, which dials usually show as 180 C. In Fahrenheit it is 350 F.
Why are there two Celsius columns in the table?
One is the exact conversion and the other is the rounded value commonly printed on oven dials. They differ by a few degrees.
How do I adjust for a fan oven?
Many recipes lower the temperature by about 20 C. Enter the number of degrees in the advanced options to see the new setting.
Does the page cover marks above 9?
No. The table stops at 9, which is the highest mark on most ovens.