How to use the convection oven conversion calculator
- Choose Fahrenheit or Celsius and enter the recipe temperature and recipe time for a conventional oven.
- Check the temperature reduction in degrees Fahrenheit and the shorter time percent. They start with rule of thumb values that you can change.
- Read the convection temperature and the converted time, and start checking the food early.
- Judge doneness by the food itself, since every oven runs a little differently.
Formula
Convection temperature = recipe temperature - temperature reduction
In Celsius the reduction is 5/9 of the Fahrenheit reduction you enter
Convection time = recipe time x (1 - shorter time % / 100)
Both adjustments are rules of thumb that you control. Nothing here is a fact about your oven.
375 F for 40 minutes
With a reduction of 25 degrees Fahrenheit and a time that is 10% shorter, a recipe at 375 F for 40 minutes becomes 350 F for 40 x 0.90 = 36 minutes. Start checking the food a little earlier still.
In Celsius, 180 C with the same 25 degree Fahrenheit reduction subtracts 25 x 5 / 9 = 13.9 degrees, giving 166 C to the nearest degree. If you enter a 50 degree reduction and 20% shorter time for 425 F and 25 minutes, the result is 375 F for 20 minutes.
Rules of thumb you can change
Cooks often lower the temperature and shorten the time when a fan circulates the hot air, because the food cooks faster. The starting values of 25 degrees Fahrenheit and 10% are examples, not facts about your oven, and your manual or experience may suggest different numbers. Edit both boxes until the result matches what works for you.
Because Celsius degrees are smaller than Fahrenheit degrees, the tool converts the reduction by 5/9 rather than subtracting the same number, so the change is the same size in either unit.
Check early and trust the food
Time is the least reliable part of any conversion. Check the food at the shorter time, then add a few minutes as needed. The color, the feel and a thermometer in the center tell you more than a clock does.
A similar rule applies to the air fryer, covered by the air fryer conversion calculator. To move a recipe to another pan, use the baking pan size converter, and for slow cooking see the slow cooker conversion calculator. Unit changes are in the cooking measurement converter.
Assumptions and limits
- The temperature reduction is in degrees Fahrenheit and the shorter time is a percent, and both are your choice.
- Celsius results use 5/9 of the Fahrenheit reduction and are rounded to the nearest degree.
- Your oven may run hotter or cooler than its dial.
- Food safety temperatures and recipe science are not modeled.
Frequently asked questions
How do I convert a recipe to a convection oven?
Lower the temperature and shorten the time. With the example 25 degree Fahrenheit reduction and 10% shorter time, 375 F for 40 minutes becomes 350 F for 36 minutes.
Should I always reduce the temperature?
That is a common habit but not a rule. Change the reduction to zero if your recipe or oven manual says to use the same setting.
Why does the Celsius reduction look smaller?
A Celsius degree is larger than a Fahrenheit degree, so a 25 degree Fahrenheit drop is about 13.9 degrees Celsius.
When should I check the food?
Check early, around the converted time or a little before, and judge by the food itself, since ovens differ.