Carry-on bags for budget airlines: how to check, pack and avoid gate fees

The sizer at a budget airline gate decides whether your trip costs what you booked or quite a lot more. A bag that "should fit" is not the same as a bag that passes when a gate agent is watching. See also the luggage guides and the wider gear section. For which pack to live out of on a longer trip, start with how to choose a travel backpack. Product types are shown without brand names while partner links are set up, and the price tiers are a rough guide only. How partner links work is on how we make money.

Budget airlines use two kinds of allowance, and the bag you need depends on which one your fare includes. The first is a free under-seat bag. The second is a cabin bag for the overhead locker, which on most low fares is a paid extra. The numbers below come from each airline's own help pages. They differ in size, in weight and in how handles and wheels are counted.

Three things in the table matter more than the exact centimeters. First, the fare decides the allowance. Norwegian, for example, ties the overhead bag and the weight limit to the ticket type. Second, weight rules are written differently: some per bag, some combined across everything you carry. Third, the way handles and wheels are counted changes the real size of your bag. easyJet includes them, Wizz Air excludes handles and wheels as long as the wheels add no more than 5 cm, and other airlines may do something else.

Airlines update these limits, and Ryanair's own general terms and help pages describe the free bag with different dimensions. Treat any table, including this one, as a starting point and confirm on the page for your own booking before you pack.

A manufacturer's listed size is the size of an empty, flat bag. A sizer measures the bag as you will actually carry it. Measure at home, with the bag packed, before you reach the airport.

1. Pack the bag with the clothes and gadgets you plan to carry. Close every zip. 2. Measure height, width and depth with a tape measure, including handles, straps and wheels if your airline counts them. 3. Compare each dimension with the allowance for your fare. Depth is the one that usually fails, because soft bags bulge. 4. Weigh the bag with a luggage scale or a bathroom scale. If your airline lists a weight, remember the bag counts toward it. 5. If it is close, build a frame from a cardboard box cut to the inside dimensions of the sizer, and push the bag in and out the way you would at a gate.

If a bag only passes when you push hard, treat it as failing. A gate agent will not give it the benefit of the doubt, and a bag that squeezes in at home may stick in a rigid frame.

The comparison table on this page shows five bag types and how each one tends to relate to a free under-seat allowance and a paid overhead allowance. The point is the logic, not a brand.

Free under-seat fares. You need a small bag that is truly small. A personal-item pack is designed for it, but depth grows as you fill it, so pack to the allowance, not to the zip. A laptop, a jacket and a pair of shoes can push a small pack past the depth limit.

Paid overhead fares. You have more room, and a boxy pack with firm sides is the most predictable. Because it holds its shape, its real size stays close to the listed size. A panel loader can work as well, but soft sides bulge, so pack it with care. A rolltop shrinks to its load when rolled down and suits wet trips, though you pack it from the top.

Wheeled cases. A wheeled case is comfortable on smooth floors, but wheels and handles count toward the limit on some airlines. Check whether the airline measures them, and remember that a rigid shell cannot squash into a frame.

Most failures come from how a bag is packed, not from its size on paper. The same pack can fail with a stuffed front pocket and pass when those items move to the middle. These habits make the difference:

• Pack the middle, not the pockets. Heavy, bulky items go in the main compartment, close to your back. Keep front pockets for flat things.

• Use cubes and squeeze them. Compression cubes keep the load square, which is what a sizer measures.

• Wear the bulky layer. A jacket and your heaviest shoes on your body do not count toward the bag's size. Weight rules vary, so check whether your airline weighs only the bag or also what you carry.

• Tighten every strap before the gate, including side compression straps and a tucked-away hipbelt.

• Weigh it at home and again after you buy souvenirs.

Keep a short list of what must go in the under-seat bag in any case: passport, phone, medication, a charger and anything fragile. If your bag is moved to the hold at the gate, you do not want those items inside it.

The rules at the gate are simple, even if the experience is not. easyJet says it checks cabin bag sizes before boarding, and that a bag over the limit, or a large cabin bag brought without the right booking, will be checked into the hold with charges. Ryanair says a bag that does not fit the sizers will be refused at the gate or, where available, placed in the hold for a fee. Wizz Air says exceeding the dimensions means extra fees.

That gives you three options if your bag fails. You can pay the hold fee, you can repack and move items into your pockets or a second bag, or you can leave something behind. None is pleasant, and the first is the most expensive. easyJet states it is always cheaper to add a large cabin bag online than at the boarding gate, so the best moment to decide is when you book, not when you queue.

Carry the bag by the handle rather than on your back, keep it close to your body, and do not put it down in a sizer queue until you are asked. That is a courtesy to other passengers rather than a trick, and it keeps your bag from looking larger than it is.

Many travelers buy the bag first and discover the problem at the airport. Reverse the order. Look at the fare you want, the add-ons the airline offers and the weight rule for your ticket type. Add up the total cost of the fare plus the bag option and compare it with the next fare up. On some routes the difference is small. On others the cheapest fare with a free under-seat bag is the right choice, as long as you pack for it.

Consider your trip, too. A weekend away needs a small pack and a free allowance. A two-week trip with laundry on the way can work with a cabin bag. A month on the road probably calls for a checked bag, or for a bag you are willing to check if the airline asks. If you are changing airlines mid-trip, the strictest allowance on your itinerary is the one to pack for.

The most common mistake is assuming "carry-on" means one size. It does not. The second is measuring an empty bag. The third is forgetting that handles, wheels and external pockets can add to the size, and that some airlines count them while others do not. The fourth is assuming the weight limit is per bag when it is combined, or the other way round.

Other mistakes are quieter: buying a pack that fits only when half full, relying on a soft bag to squash into the frame, and leaving fragile or essential items in a bag that might be moved to the hold. If you fly several budget airlines in one trip, write down the limit for each and pack to the smallest.

If your fare includes a checked bag, or your fare includes a cabin bag and your bag is well within the limit, you do not need a pack built around a sizer. Any comfortable bag that fits your allowance will do, and the backpack guide covers how to choose one.

You also do not need to buy anything if the bag you own already passes. Measure it packed, including wheels and handles for a case. A tape measure and a kitchen scale at home will tell you more than any product description, and the money you save is better spent on the trip. For trip planning beyond the airport, see the transport guides.