Air fryer conversion
Type the oven temperature and this shows what each of five published rules tells you to set — because no two of them agree, and the one everybody repeats is twice what the manual in the box says. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
Five publishers, and no two agree
There is no standard for this. There is a manufacturer's rule, a different rule from the same manufacturer in another market, two American university extension services, and the figure British articles repeat. Every one of them was read at its own address, and the table above converts your temperature under all five.
The spread is not a rounding. On a 200 °C recipe the five answers cover about eighteen degrees.
The same company says two different things
The Ninja AF451UK manual, sold in Britain, says to reduce the temperature by 10 °C. The Ninja AF100 owner's guide, sold in America, says 25 °F — which is a drop of nearly fourteen degrees Celsius, not ten.
Neither manual says anything at all about cooking time. Both were searched for a sentence shortening it and there is none. Every “twenty per cent less time” you have read comes from somewhere other than the people who made the machine.
Why 25 °F is not −3.9 °C
Three of these five give their reduction in Fahrenheit, and a reduction is a difference rather than a temperature. A difference converts with the ratio alone — multiply by five ninths — and not with the offset that converts an actual temperature.
Put 25 °F through the temperature conversion and you get −3.9 °C, which is a small plausible number and completely wrong. The right answer is 13.9 °C. This page does the second one.
The British 20 °C rule, and the chart that does not follow it
The figure everybody repeats in Britain is twenty degrees, and it does have a publisher: an air fryer cookbook from Mid and East Antrim Borough Council, produced by its Community Health and Wellbeing Team with the recipes reviewed by Northern Health and Social Care Trust dietitians. It says to reduce the temperature by 20 °C and the time by between a quarter and one fifth.
Its own conversion chart does neither. Both tables were checked row by row rather than sampled:
- The time chart has eleven rows, from ten minutes to an hour. Every single one takes off exactly one fifth. The quarter end of the stated range is never used.
- The temperature chart has five rows, and not one of them drops 20 °C from a conventional oven. Four drop forty and the fifth drops thirty. The twenty only appears if you read across from the fan column — and the top row breaks even that, dropping ten.
So the sentence says “converting conventional oven recipes” and the chart beneath it is doing something else. None of which makes the council wrong about air fryers; it makes the twenty-degree rule a number worth knowing the provenance of.
If your oven is a fan oven, the rule is written for somebody else
Every one of these five rules says conventional or traditional. A fan oven already runs about twenty degrees cooler than a conventional one for the same result, so applying a rule written for a conventional recipe to a fan setting takes roughly the same twenty degrees off twice.
Most British ovens are fan ovens and most recipes are still written in conventional temperatures, so this is the usual case rather than a corner of it. Tell the box which yours is and it will say what it did.
And check the food, not the clock
Every source that gives a time says some version of the same thing: start looking early. Air fryers vary more than ovens do, the basket is small enough that how full it is changes the answer, and none of these rules knows what you are cooking.