Underseat Bags Explained: Sizes, Rules and Best Picks for UK Airlines

You’ve never really thought about underseat bag dimensions until you’re standing at a gate with a bag that's 2 cm too wide and a Ryanair staff member pointing at the metal sizer. Then it becomes a very important concept, very quickly.

The underseat bag is the free bag on most budget airlines. It goes under the seat rather than in the overhead locker and it's the only thing included on a standard fare with Ryanair and easyJet without paying anything extra. Get the size right and you're through the gate without a conversation. Here's what you need to know before you buy.

What Is an Underseat Bag?

An underseat bag, sometimes called a personal item, is a small piece of luggage stored in the footwell under the seat in front of you rather than the overhead locker. Most UK budget airlines include one free on every fare. It is the baseline allowance. Everything else, including overhead locker access, usually costs extra.

It stays within reach for the whole flight, which matters if you need your charger, medication or headphones mid-journey. If you're looking for a bag built specifically for this, Lugg has a dedicated underseat cabin bag collection sized to the exact dimensions of the strictest budget airline allowances.

Airline Underseat Bag Sizes: What Each UK Carrier Allows

The rules vary more than most people realise, and the gap between airlines is wide enough to matter when you're choosing a bag.

Ryanair’s free underseat allowance is 40 x 30 x 20 cm with no stated weight limit. It’s the strictest standard among UK budget carriers and the one to design around if you fly multiple airlines, since a bag built to Ryanair’s dimensions fits within every other carrier’s allowance. Gate staff use a physical metal sizer and they do use it. A bag that is even 1 cm over in any direction is a problem, not a rounding error. Getting it wrong at the gate costs up to £70.

easyJet is considerably more generous at 45 x 36 x 20 cm and up to 15 kg. That’s a meaningfully bigger bag included free on every standard fare, which catches a lot of people out when they’ve bought a 40 x 30 x 20 cm bag unnecessarily. Overhead locker access on easyJet requires a paid add-on or an easyJet Plus membership.

Wizz Air allows 40 x 30 x 20 cm at up to 10 kg free, same dimensions as Ryanair with a stated weight limit. Wizz Priority unlocks a larger overhead bag at 55 x 40 x 23 cm.
Jet2 is quietly one of the most generous budget carriers going. Every fare includes a full-size overhead cabin bag at 56 x 45 x 25 cm plus an underseat personal item at 40 x 30 x 20 cm. Two bags, both included, no add-on required.

British Airways and Virgin Atlantic both include an underseat personal item alongside their cabin bag allowance, but the depth limit is 15 cm rather than 20 cm. A standard 40 x 30 x 20 cm underseat bag is too deep for these airlines’ underseat space and would need to go in the overhead locker instead. Worth knowing before you assume one bag works everywhere.

For a full breakdown of every UK airline's cabin bag allowance including overhead bags, see our full airline size guide.

How Much Fits in an Underseat Bag?

More than you'd think, if you pack with some intention. A well-packed 40 x 30 x 20 cm bag gives you roughly 20 to 24 litres of usable space, which is enough for a one to two-night trip without checking anything in: tech, a change of clothes, toiletries within the 100 ml liquid rules and the things you actually need on the flight.

The mistake most people make is treating it like a small suitcase and packing from the bottom up. The better approach is to start with what you need during the flight, pack that first and fill around it. Passport, medication, charger, headphones. Everything else is secondary.

Thinking of doing a longer trip cabin-only? Read our guide on packing two weeks in a cabin bag.

Wheels or No Wheels?

A wheeled underseat bag is worth getting. Rolling through a terminal is considerably easier than carrying a bag by hand, especially on the longer walks between check-in and gate that some airports seem to specialise in. The trade-off is that the wheels count toward the overall dimensions on many bags, which is where people get caught out.

All three Lugg underseat bags featured below have detachable wheels. You can roll through the terminal, remove the wheels before the gate sizer if needed and slide the bag under the seat without any drama. For Ryanair specifically, removing the wheels before the sizer is the safest approach.

UK Airline Underseat Allowances at a Glance

Always check your airline’s website before travelling as policies change. Ranked from strictest to most lenient, with Ryanair at one end and Jet2 and British Airways at the other.

The Best Lugg Underseat Bags for UK Airlines

Jetset Underseat Bag in Slate Blue

The straightforward choice. ABS hard shell, detachable wheels, 360 degree spinners, water-resistant coating and a standard locking system. Compatible with easyJet, Jet2, Ryanair, Wizz Air, Vueling, TUI, Emirates, Eurowings and Norwegian. Eight colourways to choose from. If you want a reliable underseat bag that does the job on most UK budget airlines without fuss, start here.

Jetset Underseat Cabin Bag in Slate Blue

Vacay Underseat Bag in Stone

The most colour-forward range in the collection, with over ten colourways and the lowest starting price of the three. Same ABS hard shell, same detachable wheels, same airline compatibility as the Jetset. Stone is an easy pick if you want something that works for a work trip on Monday and a weekend away on Friday without looking out of place at either.

Vacay Underseat Cabin Bag in Stone

Sky Rover Underseat Bag in Oxblood

The most premium finish of the three, with a more structured shell and a colourway that stands out at the carousel rather than disappearing into a sea of black bags. ABS hard shell, detachable wheels, 360 degree spinners, water-resistant coating. For Ryanair, remove the wheels before the gate sizer. Everything else about it is the same as the Jetset and Vacay, just turned up a notch.

Sky Rover Underseat Cabin Bag in Oxblood

FAQs About Underseat Bags for UK Airlines