What this calculator does
The usual rule is twenty degrees lower and twenty per cent less time, so a recipe calling for 30 minutes at 200 °C becomes 24 minutes at 180 °C. In Fahrenheit the conventional drop is 25 degrees, which turns 400 °F into 375 °F. Both the drop and the time cut are fields here rather than fixed numbers, because they are a starting point and models differ more than the rule admits.
The reason the rule works at all is that an air fryer is a small fan oven. Moving air transfers heat faster, so the same browning happens at a lower set temperature, and the small cavity reaches it sooner. The reason the rule fails is also the small cavity: it depends far more on food sitting in a single layer with air moving around it than on anything the dial says. Doubling the quantity does not keep the time, and that is the adjustment most recipes do not mention.
The formula
The temperature is oven temperature − reduction and the time is oven time × (1 − time reduction). The reduction is read in whichever scale you select, so 20 in Celsius and 25 in Fahrenheit both mean the conventional drop, and the result is shown in both scales regardless. The first check is a percentage of the converted time, because the failure mode with an air fryer is overcooking something that would have been fine in an oven for another ten minutes.
| Term | Meaning |
|---|---|
| Temperature reduction | How far below the oven setting to run. Conventionally 20 °C or 25 °F. |
| Time reduction | Percentage off the oven time. Conventionally about twenty per cent. |
| Single layer | Food arranged so air reaches all of it. The real driver of air fryer results. |
| First check | When to open and look, deliberately earlier than the converted time. |
The inputs explained
| Field | What to enter |
|---|---|
| Oven temperature | Temperature the recipe gives for a conventional oven. |
| Temperature scale | Which scale you are working in. The reduction below is read in the same scale. |
| Oven time (min) | Time the recipe gives for a conventional oven. |
| Temperature reduction (degrees) | How far to drop the temperature, in the scale you chose. Twenty in Celsius or twenty-five in Fahrenheit is the usual rule. |
| Time reduction (%) | Percentage to take off the time. Twenty per cent is the usual starting point. |
| First check at (% of the time) | How far through the converted time to check. Seventy per cent is early enough to save something. |
When to use it
Converting a recipe you know
Enter the oven figures and start from the converted ones. Note what the machine actually needed, since that correction will hold for the next recipe.
If the recipe is already fan-forced
A fan oven figure is already reduced, so a second full reduction will undercook. Drop the reduction to something small or to zero and keep the time cut.
Cooking more than one layer
Add time rather than temperature, and shake or turn partway. More heat on a crowded basket browns the outside before the middle is done.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What temperature replaces a given oven setting?
Only the oven temperature changes.
| Oven temperature | Air fryer temperature | In Fahrenheit |
|---|---|---|
| 160 °C | 140 °C | 284 °F |
| 180 °C | 160 °C | 320 °F |
| 200 °C | 180 °C | 356 °F |
| 220 °C | 200 °C | 392 °F |
| 240 °C | 220 °C | 428 °F |
How long should an air fryer recipe run?
Only the oven time changes.
| Oven time | Air fryer time | Time saved | First check at |
|---|---|---|---|
| 10 min | 8 min | 2 min | 6 min |
| 20 min | 16 min | 4 min | 11 min |
| 30 min | 24 min | 6 min | 17 min |
| 45 min | 36 min | 9 min | 25 min |
| 60 min | 48 min | 12 min | 34 min |
Questions
Why twenty degrees?
Because the moving air transfers heat faster than still air, so a lower set temperature produces the same surface browning. It is the same adjustment people make between a conventional and a fan oven, and it is a convention rather than a physical constant, which is why it is editable here.
My recipe is already fan-forced. Do I still drop it?
Mostly no. A fan-forced figure has already had the reduction applied once, so dropping it again will undercook. Keep the time reduction, since the small cavity still cooks faster, and set the temperature drop to zero or close to it.
Do I need to preheat?
For most things it makes little difference because a small cavity heats in a few minutes, but it matters for anything that should sear on contact. The conversion here assumes you follow whatever the recipe said about preheating.
Why does doubling the food not double the time?
Because the limit is airflow rather than energy. A single layer with space around it cooks at the rate the chart suggests, and a crowded basket steams instead. Add time, shake partway, and expect a batch of two layers to take more than twice as long as one.
Is the food safe at the lower temperature?
Safety is about the internal temperature the food reaches, not the setting on the dial, so check meat with a thermometer exactly as you would from an oven. A lower air temperature for a shorter time can still bring the centre to the same place, but only a thermometer confirms it.
For the other direction of recipe conversion there is the microwave wattage converter. Turkey roasting and thawing and ham cooking time cover the oven times this page starts from.