The 60% rule: why you can never fill it all the way
The rated volume on the box — 5.5L, 6L, etc. — is the total interior volume of the basket, not how much food you can cook in one go. The air fryer works by blasting hot air around all exposed surfaces of the food. If pieces are touching or layered on top of each other, air can't reach the covered surfaces and those parts steam rather than crisp.
In practice, this means you can only fill the basket to about 60% of its rated capacity. A 5.5L air fryer has around 3–3.5L of practical cooking capacity — a single layer of chicken thighs with space between each piece.
This is why it's almost always better to size up when you're uncertain. The difference in countertop footprint between a 4L and a 5.5L is small. The difference in whether you cook dinner in one batch or two is real.
Basket vs. oven-style: which is better?
Basket air fryers (the most common type) have a pull-out drawer with a mesh or perforated basket. The food sits in the basket, and hot air circulates both above and below through the mesh. This 360-degree airflow produces better crisping results, especially on the bottom of food.
Oven-style air fryers look like small countertop toaster ovens with one or two wire racks. They hold more food and are easier to load without having to tip the drawer, and many include a rotisserie function. The tradeoff: airflow is less concentrated because the chamber is larger and more rectangular.
For most people who want the crispiest fries and chicken: basket style. For families or anyone who values capacity and versatility over maximum crispiness: oven style at 9L+.
Countertop footprint: what actually fits in a kitchen
Sizes vary by brand, but as a rough guide:
- 2–3L basket — roughly the footprint of a large coffee maker. Fits most counters.
- 4–5.5L basket — roughly 30 × 30 cm footprint. The most common size sold. Fits most kitchens.
- 6–7L basket — notably larger. Measure your counter space and cabinet clearance before buying.
- Oven style 9L+ — footprint comparable to a microwave. You'll need dedicated counter space.
Also consider: air fryers need 10–15 cm of clearance above the unit for the exhaust vent. Don't store it under a low cabinet.
If you cook for two: buy a 4L, not a 2L
The 2L and 2.5L models are popular because they're inexpensive and compact. But in practice, they're limited even for one person. A chicken breast barely fits. Two portions of fries require two batches.
For two people, a 4L basket air fryer is the practical minimum for comfortable weeknight cooking. You can cook two chicken thighs, a portion of fries, or four fish fillets in one batch. The 3.5–4L range is the sweet spot for couples.