Carry-On Size Calculator

The two numbers that decide it

Every airline publishes a carry-on limit as three sides, such as 22 by 14 by 9 inches. That is the first check. The second is linear inches, which is the three sides added together, and most US carriers cap it at 45. A bag has to pass both. A 26 by 12 by 7 inch duffel adds to 45 and still will not slide into a 22 inch sizer, because the longest side is 4 inches over.

The measurement includes wheels, handles, side pockets and any strap that sticks out. This is where most bags fail, because a suitcase sold as a 22 inch carry-on usually measures 24 inches from the floor to the top of the extended handle. The 22 inch figure refers to the body, and the gate agent measures the whole object.

Pack the bag before you measure it. An empty soft bag measures one thing and a full one measures another, and the front pocket that bulges 1.5 inches when it holds a laptop is the difference between fitting the sizer and paying a gate fee. Measure the tallest, widest and deepest points, round up to the next half inch, and use those three numbers.

Worked example: a 24 inch roller bag

A common 24 inch roller measures 24 by 16 by 10 inches with the wheels and handle included. Add the sides: 24 plus 16 plus 10 is 50 linear inches. Against the 45 inch limit on American, Delta and United, that is 5 inches over, and the bag fails on all three sides, since the limit is 22 by 14 by 9.

Put the same bag on Southwest or Frontier and it passes, because both allow 24 by 16 by 10 exactly. Nothing about the bag changed. The airline did. That is the single most useful thing this calculator shows: a bag is not a carry-on in the abstract, it is a carry-on on a specific airline.

The same arithmetic on smaller bags makes the 45 inch rule concrete. A 21 by 14 by 8 bag is 43 linear inches, 2 under the limit. A 22 by 14 by 9 bag is exactly 45. A 23 by 15 by 9 bag is 47, which is 2 over, and the width is 1 inch past the 14 inch side limit as well. A 26 by 18 by 11 bag is 55, which is 10 over and 5 over even on Southwest.

Carry-on limits by airline

These are the published cabin bag limits for the airlines US travelers use most, in inches with wheels and handles included. The linear column is the three sides added, and it is the number the sizer bin enforces alongside each side.

The FAA's carry-on baggage guidance puts the usual ceiling at 45 linear inches and points out that the airline sets the actual rule, so the chart above is the place to check before a flight. Sizes and fees move: carriers change limits every few years, and several international carriers tightened theirs to fit newer overhead bins.

One warning about shopping by linear inches alone. easyJet's limit is 49.5 linear inches, which sounds generous next to American's 45, but the extra room sits in the width: 17.7 inches against 14. A tall narrow bag can reach 49 linear inches and still fail American on height, and a wide bag can pass easyJet and fail American on width. The linear total is a second check, never a shortcut.

22 x 14 x 9 versus 21 x 14 x 8

Two numbers come up again and again in carry-on shopping, and they are not interchangeable. The 22 by 14 by 9 figure is the US major standard, and it is 45 linear inches. The 21 by 14 by 8 figure is the tighter international and budget-carrier standard, and it is 43 linear inches. A bag built to 22 by 14 by 9 will fail a 21 inch sizer, and a bag built to 21 by 14 by 8 fits everywhere.

Why the smaller number exists at all comes down to the bins. Narrow-body aircraft flown by low-cost carriers in Europe and Asia have smaller overhead compartments, and the sizer at the gate is built to the bin, not to a marketing standard. When you see 21 by 14 by 8 on a product page, the manufacturer is aiming at the tightest common limit so the bag can be sold in more markets.

The practical rule for a US traveler who flies mostly domestically is to buy 22 by 14 by 9 and check the bag against the specific airline before an international trip. The practical rule for anyone flying a European budget carrier is to buy 21 by 14 by 8, or to accept that a 22 inch bag will be gate-checked and charged. Soft-sided bags have an advantage here, since an inch of give often gets them into a sizer that a hard shell cannot enter.

Does the personal item count as a bag

Yes, it counts as a piece, and that is the part people get wrong at the gate. The standard US allowance is one carry-on that goes in the overhead bin plus one personal item that goes under the seat in front of you. Both are free on the major carriers. A purse, a laptop bag, a briefcase or a small backpack all count as the personal item, not as an extra.

What that means in practice is that you get two pieces, not three. A carry-on roller, a backpack and a purse is three pieces, and the purse becomes a third item that has to be consolidated or checked. On a basic economy fare that excludes the carry-on, the personal item is the only free bag, and it still has to fit under the seat.

The American Airlines carry-on page is a good example of how the two allowances are written, and Delta's page says the same thing without publishing a personal item size, which is why a tape measure and the seat in front of you are the real test.

How to measure a bag the way the gate agent does

Measure the bag packed, zipped and standing up. Put the tape at the floor, at the point where the wheels touch, and run it to the highest point of the handle. That is the height, and it is usually 2 inches more than the number on the product page. Then measure the widest point across the body including side pockets, and the deepest point including the front pocket when it is full.

Write the three numbers down and round each up to the next half inch. Gate agents do not measure to a quarter inch, but the sizer bin is a fixed frame, and a bag that is 0.25 inches over on paper will often still slide in while a bag that is 1 inch over will not. The TSA what can I bring list covers what goes inside the bag, which is a separate question from whether the bag itself fits.

Check the expansion zipper. A bag with an unzipped expansion panel is 1.5 to 2 inches deeper, and that is enough to fail a sizer that the same bag passes when closed. Check the wheels too: spinner wheels on a hard shell add 2 inches of height, and a bag sold as a 21 inch cabin bag measures 23 inches with them on.

What happens at the gate if it does not fit

The gate agent points at the sizer, and the bag either slides in or it does not. If it does not, the bag gets checked to your destination and you pay a gate fee, commonly $65 to $100 on a US major. That is more than the fee you would have paid to check the bag online before the flight, and on a basic economy fare the gap is larger.

One thing softens the blow. A bag that is 1 inch over on a soft-sided frame often passes, because the sizer has some give and the agent is looking at the flight, not at a tape measure. That is not a plan, but it explains why the same bag gets through on one trip and not the next, and why the traveler next to you with a hard shell gets stopped.

The reliable approach is to buy to the tightest airline you fly, pack to that size, and measure once at home with the bag full. A 21 by 14 by 8 bag is 43 linear inches and clears every limit in this table except the width on easyJet, and it removes the gate conversation entirely.

Airline limits and fees change without notice. Confirm the size on your airline's baggage page before you fly, since the sizer at the gate is the only measurement that counts.