Air Fryer Conversion Calculator

Why air fryers need a lower temperature and shorter time

An air fryer is really a small, powerful convection oven: a fan circulates hot air tightly around the food in a compact basket, so heat transfers much faster than in a full-size oven. Cooked at the same temperature as the oven recipe, food in an air fryer would burn on the outside before the inside caught up — so the standard fix, cross-checked across UK recipe conversion guides, is to drop the temperature by about 20°C (or 25-30°F) and cut the time by about 20%.

It is a rule of thumb, not a law of physics: basket size, how crowded it is, and your particular air fryer model all shift the real number by a few minutes either way. Treat the calculator's output as your starting point, then check the food a little before the time is up.

Fan oven vs conventional oven: the conversion changes

This is the detail most air fryer converters get wrong. A fan-assisted (convection) oven already cooks roughly 20°C cooler than a conventional (static) oven for the same dish — that is standard UK cooking knowledge, and it is why recipe books often print two temperatures side by side. If your recipe temperature is already the fan-oven figure, applying the full -20°C air fryer reduction on top would double-count that gap and leave your air fryer running too cold.

So the calculator above applies the full reduction (-20°C / -25°F) when you select conventional, and only half of it (-10°C / -15°F) when you select fan — because half the usual air-fryer gap is already baked into a fan-oven temperature. The time reduction (-20%) is the same either way, since it reflects the smaller, faster-circulating basket rather than the fan/conventional difference.

Do you need to preheat an air fryer?

Most modern air fryers heat up in 2-3 minutes, much faster than a full oven, and preheating for that short window noticeably improves crisping — especially for frozen or breaded food like chips and fish fingers. It is not always essential (some manufacturers build preheat into the cook cycle automatically), but if your model does not, a 2-3 minute preheat before adding food is worth the small time cost.

Reading the reference table

The table below gives direct air fryer settings published for common UK foods — these are the numbers people actually use, cross-checked against a UK air fryer cooking-times guide and a homemade-chips recipe, rather than numbers derived purely from the oven-conversion rule. Use the calculator above when you are starting from a specific oven recipe; use the table when you just want to cook one of these foods and skip the maths.

Frozen food generally needs a touch longer than fresh, and thicker cuts of meat need longer than thin ones — always check the food is piping hot throughout, and that chicken has reached an internal temperature of 75°C, in line with Food Standards Agency guidance.

Common mistakes when converting a recipe

The two biggest causes of soggy or unevenly cooked air fryer food are not maths errors: overcrowding the basket (hot air cannot circulate around packed-in food, so it steams instead of crisping — cook in batches if needed) and skipping the shake or flip halfway through, which most oven recipes never mention because a full oven heats more evenly all around the tray.