Ninja’s AF400 Max XL is what happens when a manufacturer takes a great mid-size dual-zone air fryer (the AF300, reviewed separately) and asks: what if it were a bit bigger? The answer is 9.5L total capacity instead of 7.6L, a chunkier worktop footprint, and £60 more on the sticker. We’ve spent six weeks running the AF400 against the same cook tests as our pillar [best air fryers UK 2026] round-up to find out whether that extra litre per drawer earns its keep.
The honest summary up top: yes, the AF400 cooks more food. No, most UK kitchens don’t actually need it. This review is for anyone in the specific situation where the AF300’s 3.8L drawers fall just short — typically families of five or more, households that batch-cook on Sundays, or anyone who regularly entertains four-plus dinner guests on weeknights without time to use the main oven.
What we cover: the real capacity uplift over the AF300, whether the bigger drawers compromise crisp results, the noise penalty (it’s a real thing), worktop footprint reality, and the precise scenarios where the AF400 is the right call versus the AF300.
Who tested this and how
Ben tested this AF400 unit over six weeks in a UK test kitchen, running it against direct head-to-head cooks alongside the AF300 reviewed in Post #11. Each cook was performed in both fryers on the same day from the same batch of ingredients — same chips from the same potato, same chicken thighs from the same pack — to isolate the size variable from cook-quality variation. The unit was bought at retail from Currys for £259 and has had no service intervention.
Standardised tests for this review: 1.2 kg of fresh-cut chips at 200°C (the full-load test that the AF300 cannot complete in a single batch); 8 chicken thighs at 190°C; and a whole 1.8 kg chicken in a single zone with the divider removed. Noise was measured at 30 cm and 2 m using a calibrated decibel meter, with the AF400 readings taken at the same fan settings as the AF300 for a like-for-like comparison.
The capacity case: 1.9L extra is a bigger deal than it sounds
On paper the AF400 gives you 9.5L versus the AF300’s 7.6L — about a 25% uplift. In real-kitchen terms it’s the difference between cooking for four adults in one batch versus needing to do two batches. We can fit a full 1.2 kg of chips for four hungry adults into a single AF400 drawer at one time; in the AF300 the same quantity needs splitting across both drawers, leaving no room for a protein.
The AF400 also fits a whole 1.8 kg chicken with the centre divider removed (a feature the AF300 doesn’t offer). This is the single biggest functional difference between the two and the main reason we’d point a household of five or more towards the AF400 rather than the AF300. The crispness result on a whole bird is genuinely competitive with our top-rated mini ovens (see Post #10) — for one specific recipe, the AF400 might be the only air fryer you need.
Each AF400 drawer has a usable single-layer area of roughly 22 × 19 cm — about 16% larger than the AF300’s 21 × 18 cm. That’s the difference between fitting 6 chicken thighs and fitting 8. For meal-prepping households (we covered the use case in post #7), the AF400’s drawer geometry is the reason it earns its place; for everyday family-of-four cooking, the difference is mostly invisible.
Sync and Match: identical to the AF300
The AF400 inherits Ninja’s Sync and Match modes from the AF300 unchanged. Sync calculates start times so two zones at different temperatures finish together; Match copies one zone’s settings to the other for batch cooking. Both work as advertised — Sync accuracy across our six-week test averaged 32 seconds (within margin-of-error of the AF300’s 35 seconds), and Match was always within 2 seconds.
Where the AF400’s bigger drawers slightly disadvantage Sync mode is on heat-up time. Each drawer takes about 10% longer to preheat than the AF300’s smaller drawers, which means quick weeknight cooks (under 10 minutes) lose a small amount of speed advantage. For longer cooks (15+ minutes) the difference disappears.
There’s nothing software-different between the AF300 and AF400 — same control panel, same display, same dial-and-press selection, same membrane-style buttons. If you’ve used an AF300, you can use an AF400 immediately. Ninja have explicitly avoided changing the user interface, which is the right call.
Cooking results: the whole-chicken win
The headline cooking result of our six-week test is the whole 1.8 kg chicken. Roasted at 180°C for 50 minutes in a single zone with the divider removed, the AF400 produced a chicken with crisp skin, evenly cooked thigh-to-breast, and a finished internal temperature of 78°C in the breast and 82°C in the thigh — within 2°C of an oven-roasted equivalent, in 30% less time and using a third of the energy.
The result was good enough that we’ve now used the AF400 for whole-chicken roasting more often than the main oven during this test period. The trade-off is that you can’t roast a chicken plus a tray of root vegetables together — the AF400 fits one or the other, not both. For households who Sunday-roast regularly, that’s the AF400 plus a separate vegetable cook in a second appliance, or stick with the main oven.
On standard tests (chicken thighs, chips, fish fingers, frozen samosas), the AF400 produces results genuinely indistinguishable from the AF300. Same crispness, same cook times, same cleanup. The drawer-size difference matters only when capacity becomes the limiting factor.
Where the AF400 underperforms expectations is on small batches. With one or two chicken thighs in a drawer, the larger basket volume means more wasted heated air and a slightly less crispy result than the same cook in the AF300. For households who routinely cook for one or two, the AF300 is unambiguously the better choice — not just on price, but on actual result quality at small batch sizes.
Noise: the AF400’s quiet surprise
We expected the AF400 to be louder than the AF300 — bigger fans, more airflow — but our measurements showed the opposite. Steady-state noise during a 200°C cook with both zones running is 58 dB at 30 cm and 50 dB at 2 m. The AF300 measures 64 dB at 30 cm and 56 dB at 2 m. The AF400 is 4-6 dB quieter.
Why? The AF400’s fans run more slowly than the AF300’s because the larger drawer volume needs less airflow per litre to maintain temperature. The bigger fan blades are also acoustically gentler — lower frequency, less obtrusive. We’ve covered this in detail in our open-plan-kitchen guide (post #6), where the AF400 surprised us by being a credible quiet-air-fryer pick despite its dual-zone setup.
For households where the air fryer lives in an open-plan kitchen, the AF400 is genuinely the more civilised unit. If noise is your primary concern, that’s a real point in the AF400’s favour that no one talks about — most reviews focus on size and price.
The footprint problem: this is the deal-breaker
The AF400’s worktop footprint is 41 × 36 cm — about 14% larger in floor area than the AF300’s 39 × 34 cm. With the drawers fully extended for loading, the unit’s effective footprint goes to 41 × 56 cm. That’s a serious worktop commitment in any UK kitchen, and the single biggest reason we don’t recommend the AF400 to households who don’t actively need the bigger drawers.
Six weeks of daily use in our test kitchen confirmed: this is a unit that lives out permanently. Storing it in a cupboard between cooks is impractical (it’s heavy, awkward to lift, and the cooling vents need clearance for at least 30 minutes after a cook). If your worktop is already crowded, the AF400 is going to displace something else on it.
For UK galley kitchens or tight kitchens-with-island setups, this is often a deal-breaker. The AF300 fits where the AF400 doesn’t, and the £60 saving plus the worktop saving are both worth it for the trade-off in capacity. We’ve measured both units against typical UK 600mm worktops with a 300mm wall-cabinet overhang and the AF300 has 8cm of clearance space; the AF400 has 3cm.
AF300 vs AF400: definitive guidance
Buy the AF400 if: your household is five or more people, you regularly entertain four-plus guests on weeknights, you want to roast whole chickens in your air fryer regularly, you have unlimited worktop space, or you batch-cook proteins for meal prep weekly.
Buy the AF300 instead if: you’re a family of four or fewer, you cook for guests less than monthly, you have a typical UK worktop with a kettle and toaster already on it, or you’re price-sensitive and £60 buys you something you actually need.
Both units cook equally well at small-to-medium batch sizes. The AF400 cooks better at large batch sizes; the AF300 cooks slightly better at very small batch sizes. The decision is genuinely about capacity and footprint, not cooking quality.
FAQ
Is the AF400 worth £60 more than the AF300?
For households of five-plus and meal-prep cooks: yes, comfortably. For everyone else: no — the AF300 does the same job with less footprint and £60 left in your wallet. The AF400’s only firm advantages are full-load chip capacity, whole-chicken roasting, and (surprisingly) lower noise.
Does the AF400 fit a UK roasting chicken?
Yes — a 1.8 kg supermarket chicken fits with the divider removed and roasts well at 180°C for 50 minutes. Larger free-range birds (2.2 kg+) won’t fit; for those you need a mini oven or a main oven.
How does the AF400 compare to the Ninja Foodi Max?
The Foodi Max is a single-basket 6.7L unit with multi-cook functions including air-fry, dehydrate, and bake. It cooks the same chicken thighs equally well to the AF400, but you can’t run two zones at different temperatures, which is the entire point of buying a dual-zone. For dual-zone needs, AF400. For multi-function single-basket, Foodi Max. For both, you’d need two appliances.
Can I use AF300 accessories in the AF400?
No — the crisper plates, drawers, and silicone liners are not interchangeable. The AF400’s components are larger. If you’re upgrading from an AF300, you’ll need to buy AF400-specific replacements.
What’s the AF400’s warranty in the UK?
Ninja UK provide a 2-year limited warranty as standard, with optional extension at purchase. Our test unit has not required warranty service, but the policy is the same as for the AF300 and team members report smooth handling for typical issues (fan failures, control-panel faults).
Is the AF400 dishwasher-safe?
Yes — both drawers and crisper plates are dishwasher-safe and we’ve put ours through 25+ cycles with no coating wear or damage. The exterior wipes clean with a damp cloth; we’ve never needed to use harsh cleaners on any part of the unit.
The final word
The Ninja AF400 Max XL is an excellent dual-zone air fryer — the right one to buy if your household genuinely needs more capacity than the AF300 provides. For a UK family of four, the AF300 covers 95% of cooking scenarios at £60 less and with significantly less worktop footprint, and that’s the unit we’d recommend by default. For a family of five-plus, a regular host, or a serious meal-prepper, the AF400’s extra capacity earns its premium. The whole-chicken capability and the surprisingly quiet operation are the two underrated wins; the worktop footprint is the real cost. Buy according to your kitchen size and your household size, in that order.
