Oven to Air Fryer Conversion: The −25°F Rule and the Foods That Break It

You found a recipe that says “bake at 425°F for 30 minutes,” but you want to make it in the air fryer — faster, crispier, and without heating up the whole kitchen. The recipe gives you oven numbers. The air fryer needs different ones. Punch in the oven settings unchanged and you’ll pull out chicken that’s scorched on the outside and raw in the middle, or fries that went from golden to charcoal while you weren’t looking. This guide explains the simple rule that converts the two, why it works, and the handful of foods where the standard rule isn’t enough.

An air fryer is just a small, aggressive convection oven

There’s no frying happening. An air fryer is a compact oven with a powerful fan that blasts hot air around a perforated basket at high speed. That moving air strips away the cool boundary layer that normally insulates food in a still oven, so heat transfers faster and surfaces dry and crisp more aggressively. The small chamber also comes up to temperature almost instantly and concentrates the airflow on whatever is in the basket.

Two practical consequences follow from that, and they’re the whole basis of converting a recipe:

1. Because heat reaches the food faster, you can lower the temperature and still cook it through.
2. Because the food cooks faster, you shorten the time.

The standard rule: −25°F and ×0.8

The conversion almost every air-fryer guide agrees on is:

• Drop the temperature by 25°F (about 15°C).
• Multiply the cook time by 0.8 — roughly four-fifths, or a 20% reduction.

So that “425°F for 30 minutes” oven recipe becomes 400°F for about 24 minutes in the air fryer. A 350°F bake for 40 minutes becomes 325°F for 32 minutes. The Oven to Air Fryer Converter does this arithmetic for you and works in both directions — feed it air-fryer settings from a recipe written for the basket and it adds the temperature and time back to give you conventional oven numbers.

Why lower the temperature and cut the time, rather than just one? If you kept the oven temperature and only shortened the time, the powerful fan would brown the surface long before the interior caught up — burnt outside, cold inside. Dropping the temperature gives the heat time to penetrate while the fan does the crisping. The two adjustments work together.

The foods that break the rule

The −25°F / ×0.8 rule is a sensible default, but real foods behave differently depending on their fat, water and density. Thin, fatty, or delicate items cook even faster; dense baked goods need a gentler hand. These are the overrides built into the converter:

Food	Air fryer temp vs oven	Time vs oven	Why
Chicken wings	−20°F	×0.7	Fat renders fast; high heat crisps the skin.
Fries / chips	−25°F	×0.75	Surface starch crisps quickly — shake the basket.
Chicken pieces (bone-in)	−25°F	×0.8	Bone slows the centre; check internal temp.
Fish / shrimp	−20°F	×0.7	Delicate proteins cook in minutes.
Baked goods	−25°F	×0.85	Need time to set; cut time least.
Vegetables (roasted)	−20°F	×0.75	High heat boosts caramelisation.
Frozen ready-meals	−25°F	×0.8	Follow box temp minus 25°F.
Bacon	−50°F	×0.7	Drop temp hard to stop grease smoking.
Steak / chops	no change	×0.7	Keep the heat high for a seared crust.

Notice the two outliers. Bacon gets a much bigger temperature cut (−50°F) because rendered fat hitting a 400°F element fills the kitchen with smoke — lower and slower keeps it clean. Steak keeps the full oven temperature because you want that fierce surface heat for browning; you just spend less time at it. Baked goods get the smallest time reduction (×0.85) because cakes and cookies need time to set in the middle, and rushing them leaves a raw centre under a browned top.

Tips that matter more than the exact numbers

• Don’t overcrowd the basket. Air frying is about airflow. Pile food in two layers and the bottom steams instead of crisps. Cook in batches if you have to.
• Shake or flip halfway. Only the surfaces exposed to moving air crisp. Fries, wings and vegetables all benefit from a mid-cook toss.
• Check early on the first run. Air fryer wattage varies a lot between models. Treat the converted time as a starting estimate and check at around 60% of it the first time you make something, then note what actually worked.
• Use a thermometer for proteins. Times are guides; internal temperature is the truth. Chicken breast is done at 165°F (74°C), thighs are better around 175°F.
• Pat food dry and oil lightly. A thin spray of oil helps conduction and browning; surface moisture just delays crisping.

Converting the other direction

If a recipe is written for the air fryer but you only have a conventional oven, run the rule in reverse: add 25°F and divide the time by 0.8 (multiply by about 1.25). An air-fryer recipe of 380°F for 20 minutes becomes roughly 400°F for 25 minutes in a standard oven — and you’ll want to flip or rotate, since a still oven won’t crisp evenly the way the fan does. The converter handles this reverse calculation automatically when you switch its direction.

For the underlying temperature maths — translating between °F, °C and gas marks when a recipe uses units your appliance doesn’t — the Oven Temperature converter is the companion tool. And if you’re deciding between appliances entirely, the Slow Cooker / Instant Pot converter translates braise and stew times between the slow cooker, pressure cooker and oven.

Frequently asked questions

Do I need to preheat an air fryer? Usually only briefly. The small chamber heats in two to three minutes. Many models don’t require it at all, but preheating helps for anything you want crisp from the first second, like fries or a steak sear.

Why did my converted recipe still overcook? Most likely the basket was crowded or the model runs hot. Air fryers vary widely in real wattage. Check at 60% of the converted time on your first attempt and adjust from there.

Can I convert any oven recipe? Most roasted, baked and fried-style foods convert cleanly. Recipes with a lot of liquid (saucy casseroles, batters that flow) or large items that won’t fit the basket are poor candidates — the air fryer is at its best with dry-surfaced foods that crisp.

Start with the Oven to Air Fryer Converter, pick the food type to apply the right override, and you’ll skip the trial-and-error that ruins the first few batches.