Carry-On Luggage Rules: Sizes, Liquids, and What to Pack

Packing a carry-on the right way can save you money, time, and a lot of stress at the airport. Checked-bag fees on major US airlines now run $35 to $40 for the first bag each way, so a family of four flying round-trip can easily spend $300 just on luggage. Learn the rules once and you can skip that line, skip that fee, and walk straight off the plane at your destination.

The catch is that the rules are not as standardized as you would hope. Bag-size limits vary by airline, the liquids rule trips up even frequent flyers, and the list of what TSA actually allows is longer and weirder than most people assume. Here is everything a US traveler needs to know.

Carry-On Size Limits by Airline

There is no single federal carry-on size. Each airline sets its own, and gate agents enforce them with sizer bins when flights are full.

The unofficial industry standard is 22 x 14 x 9 inches (about 56 x 36 x 23 cm), and most legacy carriers stick to it:

• American Airlines: 22 x 14 x 9 in
• Delta: 22 x 14 x 9 in
• United: 22 x 14 x 9 in
• Alaska: 22 x 14 x 9 in
• JetBlue: 22 x 14 x 9 in

A few airlines break from the standard:

• Southwest: 24 x 16 x 10 in (the most generous of the big carriers)
• Spirit: 22 x 18 x 10 in, but the carry-on is not free unless you buy a bundle
• Frontier: 24 x 16 x 10 in, also charged separately

Two things to know. First, these limits include wheels and handles, which is exactly where rolling bags overshoot. A bag advertised as “carry-on size” is sometimes measured by the manufacturer without the wheels. Measure the whole thing. Second, an empty bag and a packed bag are different shapes. A soft-sided bag that fits the sizer empty can bulge an inch past it once it is full, and that inch is enough to get it gate-checked.

If you fly several airlines, buy to the strictest common size you use. A bag built to 22 x 14 x 9 inches will clear every major US carrier.

Personal Item vs. Carry-On

These are two different bags, and the difference matters for your wallet.

• Carry-on: the bigger bag that goes in the overhead bin.
• Personal item: a smaller bag that fits under the seat in front of you, such as a backpack, tote, laptop bag, or large purse.

On standard economy fares with the big airlines, you get both for free. The trap is basic economy. United’s basic economy allows only a personal item; bring a full carry-on and you pay a fee at the gate plus a penalty. Budget airlines like Spirit and Frontier always include the personal item but charge for the carry-on.

Personal-item dimensions are usually around 18 x 14 x 8 inches, though Spirit and Frontier are stricter (roughly 18 x 14 x 8 and smaller). A standard 15-inch laptop backpack almost always qualifies. The move on a budget fare is to pack everything into a backpack that maxes out the personal-item slot and skip the carry-on charge entirely.

The Liquids Rule: TSA 3-1-1

This is the rule that gets the most stuff confiscated. The TSA 3-1-1 rule for carry-ons is:

• 3.4 ounces (100 ml) is the maximum size for any one liquid, gel, aerosol, paste, or cream container.
• 1 quart-size clear zip-top bag holds all of them.
• 1 bag per passenger.

“Liquids” is broader than you think. It includes toothpaste, deodorant (the gel and spray kinds, though solid stick deodorant is fine), sunscreen, peanut butter, hummus, yogurt, mascara, and anything else that is spreadable or pourable. A nearly empty 8-ounce bottle is still banned because TSA goes by the container’s printed size, not how much is inside.

Three useful exceptions:

1. Medications (liquid or pill) are allowed in reasonable quantities over 3.4 oz. Declare them and they get screened separately.
2. Baby formula, breast milk, and toddler food are allowed in larger quantities when traveling with an infant; tell the officer.
3. Solid food (sandwiches, granola bars, whole fruit, snacks) has no liquid limit, so you can absolutely pack your own meal.

To clear security faster, pull the quart bag out and place it in its own bin unless you are in a TSA PreCheck lane, where liquids and laptops can stay packed. Buy travel-size toiletries or refillable 3-oz bottles, or just buy full-size toiletries after you land.

What You Can and Cannot Pack

Beyond liquids, the surprises usually involve sharp objects, batteries, and the things people forget are even in their bag.

Allowed in a carry-on:

• Laptops, tablets, phones, e-readers, and chargers
• Disposable and cartridge razors
• Scissors with blades under 4 inches (measured from the pivot)
• Knitting needles and crochet hooks
• Nail clippers and tweezers
• Solid food and snacks
• Most cosmetics that are solid or under 3.4 oz

Not allowed in a carry-on (check it or leave it):

• Pocket knives, box cutters, and loose razor blades of any size
• Scissors with blades over 4 inches
• Tools longer than 7 inches (wrenches, pliers, screwdrivers)
• Firearms and ammunition (must be declared and checked, never in a carry-on)
• Liquids over 3.4 oz outside the medical exemptions

Batteries are the reverse of what you would expect. Spare lithium-ion batteries and power banks must travel in your carry-on, not your checked bag, because of fire risk in the cargo hold. That includes external phone chargers and spare camera batteries. If a gate agent gate-checks your carry-on, pull your power bank out first.

When in doubt, the TSA “What Can I Bring?” search tool on tsa.gov gives a definitive yes or no for almost any item, and you can text a photo to TSA’s @AskTSA on social media for a fast answer.

How to Pack a Carry-On That Actually Fits

Fitting a week of clothes into a 22 x 14 x 9 inch bag is mostly technique.

1. Roll, don’t fold. Rolled clothes take less space and wrinkle less. Tightly rolled t-shirts and jeans can free up a third of your bag.
2. Use packing cubes. Two or three cubes compress soft clothing and keep the bag from turning into a pile. A compression cube for bulky items earns its space back.
3. Wear your heaviest items on the plane. Boots, jeans, and a jacket take up the most room, so wear them through the airport. The jacket doubles as a blanket and a pillow on a cold red-eye.
4. Limit shoes to two pairs. Shoes are space hogs. Wear one pair, pack one, and stuff socks inside the packed pair.
5. Decant toiletries into 3-oz bottles before you leave, or buy a single set of travel-size basics you reuse every trip.
6. Keep the essentials in your personal item: passport or ID, wallet, phone, charger, medication, and a change of underwear. If your carry-on gets gate-checked on a packed flight, you still have what you need.

A practical capsule for a 5-day domestic trip: 4 to 5 tops, 2 bottoms, underwear and socks for each day, one light layer, sleepwear, the worn outfit, and a quart bag of toiletries. That fits a standard carry-on with room to spare and means you never wait at baggage claim.

The Bottom Line

The rules come down to three numbers and one habit. Build your bag to 22 x 14 x 9 inches so it clears every major US airline. Keep liquids to 3.4 ounces in one quart bag. And always stash your valuables, medication, and power bank in your personal item in case the overhead bins fill up and your carry-on gets pulled at the gate.

Master those and you stop paying checked-bag fees, you stop waiting at the carousel, and you walk off the plane and straight out the door, which is the whole point of traveling with just a carry-on.

Frequently Asked Questions

What is the standard carry-on size in the US?

The most common carry-on size limit is 22 x 14 x 9 inches, including wheels and handles. Most major US airlines (American, Delta, United, Alaska) use this number. Southwest is more generous at 24 x 16 x 10 inches. Budget carriers like Spirit and Frontier allow 22 x 18 x 10 inches but charge for the carry-on itself. Always measure your fully packed bag, since a stuffed bag bulges past its rated size.

How much liquid can I bring in a carry-on?

Each liquid, gel, aerosol, or cream container must be 3.4 ounces (100 ml) or smaller, and all of them must fit inside one quart-size zip-top bag, one bag per passenger. That is the TSA 3-1-1 rule. Containers larger than 3.4 oz are not allowed even if they are mostly empty. Medications, baby formula, and breast milk are exempt but should be declared at the checkpoint.

Is a personal item separate from a carry-on?

Yes. A personal item is a smaller bag (purse, laptop bag, or small backpack) that fits under the seat in front of you, while the carry-on goes in the overhead bin. Most airlines let you bring both for free, but basic economy fares on United and the budget carriers often allow only the personal item unless you pay extra.

Can I bring a razor or scissors in my carry-on?

Disposable razors and razor cartridges are fine in a carry-on. Loose double-edge or straight razor blades are not. Scissors are allowed if the blades are shorter than 4 inches measured from the pivot. Pocket knives and box cutters of any size must go in checked luggage.

What happens if my carry-on is too big at the gate?

Gate agents can require you to check an oversized or overflowing bag, and at the gate the fee is often higher than checking it at the counter, sometimes $50 or more on budget airlines. On full flights, agents may also gate-check bags for free to clear bin space. Keep valuables, medication, and electronics in your personal item in case your carry-on gets pulled.