Guide · Travel · 6 models
How to choose a cabin backpack: airline dimensions, litres and layout explained
Cabin backpacks are bought by the centimetre. Ryanair and Wizz Air give you 40 × 30 × 20 cm for nothing, easyJet 45 × 36 × 20, and everything above that is a paid bag on all of them. This guide explains the rules, why the Ryanair bag changed shape, whether handles count, and how a clamshell opening differs from a top-loader — so the bag you buy is the one your airline lets on.
Start with the airline, not the bag
A cabin backpack is a container for a legal volume, and the legal volume is set by whoever you fly with most. Everything else — litres, pockets, laptop sleeves, colours — comes after. The limits below were checked on 23 September 2026; airlines change them, so check the page linked in the sources before you buy.
- Ryanair: one small bag free, 40 × 30 × 20 cm, under the seat. Priority & 2 Cabin Bags adds a 10 kg bag of 55 × 40 × 20 cm in the locker. Bags that do not fit the sizer are refused or charged.
- Wizz Air: one free bag, 40 × 30 × 20 cm, under the seat; WIZZ Priority adds a trolley bag of 55 × 40 × 23 cm.
- easyJet: one small cabin bag free, 45 × 36 × 20 cm including handles and wheels, up to 15 kg, under the seat; a large cabin bag of 56 × 45 × 25 cm only when added to the booking or with easyJet Plus.
- Jet2: one hand-luggage item up to 10 kg and 56 × 45 × 25 cm, plus a small under-seat bag of 40 × 30 × 20 cm.
- TUI: one hand-luggage item up to 10 kg and 55 × 40 × 20 cm, plus a personal item of 40 × 30 × 20 cm under the seat.
Two consequences. 40 × 30 × 20 flies free everywhere in that list — as the only bag on Ryanair and Wizz, comfortably inside easyJet’s box, and as the second bag on Jet2 and TUI. And nothing bigger than 45 × 36 × 20 is free on any of them, so a 40-litre bag is a decision to pay every time.
Why the Ryanair bag changed shape
For years the Ryanair free bag was 40 × 20 × 25 cm, and a whole category of UK backpacks was cut to it — the 20-litre Cabin Max Metz among them. The current free size is 40 × 30 × 20 cm: the same 40 cm height, 10 cm more width, 5 cm less depth. The new box is 24 litres against the old 20, so the newer bags carry four litres more for the same zero fee.
the old shape, still legal on its side
Cabin Max Metz 20L
- Capacity
- 20 L
- Height
- 40 cm
- Width
- 25 cm
- Depth
- 20 cm
- Weight
- 0.5 kg
- Material
- Recycled polyester (RPET)
Check price on Amazon.co.uk
Does an old-shape bag still pass? Yes, on its side: 40 × 25 × 20 fits inside 40 × 30 × 20 with 5 cm of width to spare. The Metz 20L is still a legal free bag on every airline above. What it does not do is use the new allowance.
Strengths
- 0.5 kg and 20 L in a shape that fits every budget airline's free bag
- Suitcase-style opening, compression straps and a trolley strap on a bag this small
- Recycled polyester with a three-year warranty from a UK company
Limitations
- Built for the old 40 × 20 × 25 rule — a 40 × 30 × 20 bag carries 4 more litres for the same fee (none)
- No laptop sleeve, only an iPad-sized compartment
- A single unit left at fetch — this listing comes and goes
Good for
- one or two nights
- a passenger who never pays for a cabin bag
- a second bag under the seat next to a paid trolley
Look elsewhere if
- a laptop bigger than a tablet
- three or four nights without a wash bag compromise
the free box exactly
Cabin Max Metz 24L
- Capacity
- 24 L
- Height
- 40 cm
- Width
- 30 cm
- Depth
- 20 cm
- Weight
- 0.6 kg†
- Material
- 600D polyester, or RPET on the recycled colours
Check price on Amazon.co.uk
The re-cut Metz 24L is the new box exactly — 40 × 30 × 20 cm, 24 litres, the same suitcase-style opening — and the shape the rest of this guide assumes.
Strengths
- Exactly the free 40 × 30 × 20 on Ryanair and Wizz Air, and inside every other airline's small-bag limit
- 24 L with a suitcase-style opening, organiser, bottle holder and trolley strap
- Three-year warranty; recycled fabric on some colours
Limitations
- The fetched Amazon listing was unavailable — colours come and go, check another colour if this one is out
- No laptop sleeve, only an iPad compartment
- Cabin Max's page and shop data disagree on weight (0.6 or 0.7 kg)
Good for
- two or three nights on a budget airline without paying for a bag
- someone replacing an old 40 × 20 × 25 bag
- a shared cabin case plus one free bag each
Look elsewhere if
- a laptop
- four nights in winter
Litres versus centimetres
Litres tell you how many nights; centimetres tell you whether it boards. The two are related only loosely, because a bag’s stated litres include pockets and the sizer does not care about pockets. The honest arithmetic: 40 × 30 × 20 is 24 litres; 40 × 20 × 25 is 20; 45 × 36 × 20 is 32, which is why bags for easyJet’s box are about 30 litres; 55 × 40 × 20 is 44. For clothes, 20 to 24 litres is two nights with discipline or three in summer, 30 is three or four, 40 to 44 is four or more or a laptop and shoes.
Soft bags are measured as packed. A 24-litre bag stuffed to bulging is a 26-litre bag with 22 cm of depth and fails a 20 cm sizer; the same bag packed to the box passes. This is the real reason compression straps and packing cubes exist.
Handles, wheels and the sizer
easyJet counts handles and wheels in its 45 × 36 × 20; Wizz Air, by our research pass’s reading of its help pages, excludes them from its Priority trolley dimensions; Ryanair’s help centre speaks of bags fitting the sizer without further qualification. For a soft backpack the question is nearly moot — the grab handle is fabric and folds flat — and that is one reason a backpack is the safer free bag than a small wheeled case, whose wheels and handle are rigid and counted on easyJet.
Layout: clamshell, top-loader, laptop
the free box with a laptop compartment
Cabin Max Manhattan 24L
- Capacity
- 24 L
- Height
- 40 cm
- Width
- 30 cm
- Depth
- 20 cm
- Weight
- 0.5 kg†
- Material
- Twill polyester with faux-suede panels
Check price on Amazon.co.uk
A clamshell or suitcase-style opening unzips the whole front panel: you pack flat on a bed, see everything, and lift out what you need. It suits packing cubes and packing to a sizer, and it is how the Metz bags and the Manhattan open. The Manhattan adds the one thing the Metz lacks — a rear compartment for a laptop up to 13 inches — inside the same free box.
Strengths
- Rear compartment for a laptop up to 13 in — the only free-size bag here that has one
- Same 40 × 30 × 20 cm and 24 L as the Metz 24L, clamshell opening, bottle pocket and trolley strap
- Looks like a work bag rather than luggage
Limitations
- Fewer organiser pockets than the Metz; no compression straps
- Cabin Max's page and shop data disagree on weight (0.5 or 0.7 kg)
- The listing's bullets are copied from the Metz — trust the photos and Cabin Max's own page
Good for
- two or three nights with a 13-inch laptop
- a bag that goes to the office on Monday
- Ryanair and Wizz Air without paying for a bag
Look elsewhere if
- a 15- or 16-inch laptop
- packing by compartments — the Metz organiser is better
a plain rucksack inside every limit
Eastpak Padded Pak'r
- Capacity
- 24 L
- Height
- 40 cm
- Width
- 30 cm
- Depth
- 18 cm
- Weight
- 0.38 kg
- Material
- 100% nylon
Check price on Amazon.co.uk
A top-loader is a sack with a zip across the top: lighter, simpler, squashier. Eastpak’s Padded Pak’r is 40 × 30 × 18 cm and 0.38 kg — inside every free limit — and packs by feel: rolled clothes at the bottom, wash bag on top. For a night or two it is fine; for four it is why clamshells exist.
Strengths
- 40 × 30 × 18 cm — inside every budget airline's free allowance with room to spare
- 0.38 kg, 100% nylon and a 30-year warranty
- Looks like a normal rucksack at the destination, not luggage
Limitations
- Top-loading sack: no suitcase opening, no organiser, no compression
- No laptop sleeve, bottle holder or trolley strap
- Soft sides bulge past 18 cm when overfilled — pack to the sizer, not the zip
Good for
- a night or two with a wash bag and a change of clothes
- someone who wants one rucksack for the commute and the flight
- a second bag alongside a paid cabin case
Look elsewhere if
- three or four nights
- anyone who packs by compartments
easyJet's larger free box
Cabin Max Metz 30L
- Capacity
- 30 L
- Height
- 45 cm
- Width
- 36 cm
- Depth
- 20 cm
- Weight
- 0.6 kg†
- Material
- 600D polyester†
Check price on Amazon.co.uk
The easyJet size is a clamshell scaled up: the Metz 30L is 45 × 36 × 20 cm exactly, which makes it free on easyJet and a Priority bag on Ryanair and Wizz — 5 cm too tall and 6 cm too wide for their free sizer.
Strengths
- 30 L in easyJet's free size — three or four nights without paying for a bag
- Suitcase-style opening and airmesh back padding
- Compression straps pull it down to a smaller sizer when half full
Limitations
- Over Ryanair's and Wizz Air's free 40 × 30 × 20 — Priority or a fee
- No laptop sleeve
- Cabin Max's own figures disagree on weight (0.6 or 0.8 kg) and material
Good for
- easyJet regulars
- three to four nights of clothes
- someone who wants one bag for the whole trip
Look elsewhere if
- Ryanair or Wizz Air flyers who never pay for Priority
- a laptop that needs its own padded sleeve
a paid bag done properly
Osprey Farpoint 40
- Capacity
- 40 L
- Height
- 55 cm
- Width
- 35 cm
- Depth
- 23 cm
- Weight
- 1.48 kg
- Load range
- 7–16 kg
Check price on Amazon.co.uk
A travel rucksack with a harness is the paid-bag category done properly: Osprey’s Farpoint 40 is 55 × 35 × 23 cm, panel-loading with lockable zips, a laptop sleeve and a hip belt, at 1.48 kg. It is a Priority or paid cabin bag on every airline here, and its 23 cm depth is 3 cm over Ryanair’s and TUI’s 55 × 40 × 20, so it must not be packed to the walls on those two.
Strengths
- 40 L with a real harness and hip belt — carries like a rucksack, not a briefcase
- Panel-loading with lockable zips and a laptop sleeve
- Osprey's guarantee covers repair for any reason
Limitations
- Never free: Priority or a paid cabin bag on Ryanair, Wizz Air, TUI and easyJet
- 1.48 kg empty — three times the Cabin Max bags
- Depth of 23 cm exceeds the 20 cm of Ryanair's and TUI's paid bag size — do not fill it to the walls
Good for
- four nights or longer
- anyone who pays for a cabin bag anyway
- Jet2 and easyJet large-bag passengers
Look elsewhere if
- free-allowance flying
- someone who wants a light bag for a night away
Trains, coaches and cars
None of this applies to rail or road. If most of your weekends away are by train, the bag is chosen by how it carries and opens, not by a sizer, and a 30 to 40-litre bag with a proper harness is the better buy. The cabin rules only bite when you fly — but when you fly a budget airline, they bite hard enough to be the whole decision.
A checklist
- Which airline most often? Write down its free box.
- How many nights? 20–24 L for two, 30 for three or four, 40 for more or for a laptop and shoes.
- Laptop? Then a bag with a compartment in the free size (Manhattan) or a paid bag with a sleeve (Osprey).
- Clamshell if you pack by outfit or use cubes; top-loader if you pack light and want the lightest bag.
- Pack to the sizer, not to the zip, and put the bag on its side if it is the old 40 × 20 × 25 shape.
Sources
Facts checked 24 September 2026
- Ryanair Help Centre — bag policy articles (search results, 2026-09-23) — Other source, checked 23 September 2026
- easyJet — Cabin bags help page — Other source, checked 23 September 2026
- Wizz Air — baggage help-centre page — Other source, checked 23 September 2026
- Jet2 — baggage FAQs — Other source, checked 23 September 2026
- TUI UK — luggage allowance page — Other source, checked 23 September 2026
- Cabin Max — Metz 24L 40x30x20 backpack product page — Manufacturer documentation, checked 23 September 2026
- Amazon.co.uk listing (Cabin Max) — Retailer listing, checked 23 September 2026
- Cabin Max — Metz 20L Underseat Cabin Bag product page — Manufacturer documentation, checked 23 September 2026
- Amazon.co.uk listing (Cabin Max) — Retailer listing, checked 23 September 2026
- Cabin Max — Manhattan 24L 40x30x20 backpack product page — Manufacturer documentation, checked 23 September 2026
- Amazon.co.uk listing (Cabin Max) — Retailer listing, checked 23 September 2026
- Cabin Max — Metz 30L Cabin Backpack product page — Manufacturer documentation, checked 23 September 2026
- Amazon.co.uk listing (Cabin Max) — Retailer listing, checked 23 September 2026
- Eastpak — Padded Pak'r product page (EK000620, UK store) — Manufacturer documentation, checked 23 September 2026
- Amazon.co.uk listing (EASTPAK) — Retailer listing, checked 23 September 2026
- Osprey — Farpoint 40 Travel Pack product page (US site, current generation) — Manufacturer documentation, checked 23 September 2026
- Amazon.co.uk listing (Osprey Store) — Retailer listing, checked 23 September 2026
What are Ryanair's cabin bag dimensions?
One small personal bag free on every fare, 40 × 30 × 20 cm, which must fit under the seat in front of you; a bag that does not fit the sizer at the gate is refused or charged. Priority & 2 Cabin Bags adds a 10 kg bag of up to 55 × 40 × 20 cm for the overhead locker. The free size used to be 40 × 20 × 25 cm; a bag of that shape still passes on its side.
Do handles and wheels count?
It depends on the airline, and the difference is why the same bag passes one sizer and fails another. easyJet says its 45 × 36 × 20 cm small bag includes any handles and wheels. Wizz Air's research-pass notes record handles and wheels excluded from its Priority trolley dimensions. For a soft backpack the question barely arises — there are no wheels and the handle is fabric — which is one argument for a backpack over a small wheeled case.
How many litres is 40 × 30 × 20?
The box itself is 24 litres, which is why Cabin Max's bags for that size are 24 L. A 40 × 20 × 25 bag is 20 L; easyJet's 45 × 36 × 20 is 32 L, and bags built for it are about 30 L. A backpack's litres are a rough guide to nights — 20 to 24 for two, 30 for three or four — but the sizer measures centimetres, and soft bags are measured as packed.
Clamshell or top-loading?
A clamshell (suitcase-style) opening unzips the whole front panel so you pack flat and find things without unpacking; a top-loader is a sack you fill from the top. Clamshells pack more predictably to a sizer and suit packing cubes; top-loaders are lighter, simpler and squash into a sizer better when half full. Most purpose-made cabin bags are clamshells; most everyday rucksacks are top-loaders.
Related reading
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Cabin backpacks for two to four nights: the sizes that fly free on Ryanair, easyJet, Jet2 and Wizz Air
A cabin backpack is bought by the centimetre, not the litre. Ryanair and Wizz Air give you 40 × 30 × 20 cm for nothing, easyJet 45 × 36 × 20, and anything bigger is a paid bag on all of them. Six backpacks that map onto those numbers — from a 0.38 kg rucksack to a 40-litre pack with a hip belt — and which trip length each one honestly covers.
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Packing cubes for a cabin bag or a medium suitcase: four sets, compression or not, sized to the bag you actually own
Packing cubes are mostly the same idea in different fabric: a zipped rectangle that turns a heap of clothes into a brick. The differences that matter are whether the cube has a second zip that compresses the brick, whether you can see into it, and whether its largest size fits flat in a 40 × 30 × 20 cabin bag. Four sets compared on exactly those things.