What Not to Pack in a Carry-On

Almost everything taken off passengers at a security checkpoint falls into three groups: liquids over the limit, things with a blade, and batteries in the wrong bag. Get those three right and you will essentially never be stopped. Everything else on this page is detail and myth-correction.

Two framing points before the list. First, TSA screens what is inside your bag; your airlinedecides how big the bag can be. Those are separate rules from separate organizations, and confusing them is the reason people arrive at a gate having solved the wrong problem. Second, rules and item lists change, and the authority is always the issuing agency’s own current page — ours are cited at the bottom.

1. Liquids over 100 ml

This is the single largest category and it accounts for most surrendered items. The rule: liquids, aerosols, gels, creams and pastes in containers of 3.4 ounces (100 ml) or less, all fitting in one quart-size clear zip-top bag, one bag per passenger.

The limit is on the container size, not on how much is in it. A half-empty 6 oz bottle is not allowed, which is the most frequently misunderstood part of the whole rule and the reason people lose expensive sunscreen.

What counts as a liquid, and catches people:

• Toothpaste, sunscreen, deodorant that is a gel or a spray (a solid stick is not a liquid)
• Yogurt, hummus, soup, jam, peanut butter, soft cheese
• Mascara, liquid foundation, lip gloss
• Aerosol dry shampoo and hairspray
• Snow globes — genuinely, and they are almost never under 100 ml

The exemptions worth knowing: medication in reasonable quantities, baby formula and breast milk, and medically necessary liquids can exceed 100 ml, but should be declared at the checkpoint and may be screened separately. The full treatment is our TSA liquids rule guide.

The structural fix is to stop packing liquids: a shampoo bar, solid deodorant, a conditioner bar and toothpaste tablets are not liquids and do not compete for space in the quart bag. On a long carry-on-only trip, that one change frees more room than any packing technique.

2. Sharp things

The pattern is enclosure. If a blade is captive inside a housing, it usually travels; if it can be got at, it usually cannot. The multitool is the item people lose most often, because it lives in a bag pocket and is forgotten.

3. Batteries — and the rule that runs backwards

Everything else on this page says “put it in the checked bag.” Batteries are the exception, and it is the exception that catches out otherwise careful packers: spare lithium batteries and power banks must travel in the cabin and are prohibited in checked baggage.

The thresholds: up to 100 Wh needs no approval; 101–160 Wh needs airline approval and is limited to two spares; above 160 Wh is forbidden on passenger aircraft. To convert, watt-hours = (mAh ÷ 1,000) × 3.7, which puts a 20,000 mAh bank at about 74 Wh and a 30,000 mAh bank over the line.

The situation that causes the most trouble is a gate-check: the bins are full, a crew member takes your carry-on at the door, and your bag becomes a checked bag with a prohibited item in it. Take the batteries out before you hand it over — and your passport and medication while you are in there. The full guide is power banks and lithium batteries on planes.

4. Flammables, pressurized and self-defense items

Smaller categories, but absolute ones:

• Lighter fluid, camping fuel, gas canisters— banned from both bags, not just the cabin.
• Pepper spray and mace— not in the cabin; checked-bag rules vary by carrier and destination, and several countries ban possession outright.
• Fireworks, flares, sparklers— banned from both bags.
• Large aerosols— even under 100 ml, some are restricted by content rather than volume.
• Bleach, drain cleaner, strong solvents— banned from both bags.

The general test: if a thing’s job is to burn, spray under pressure, or incapacitate a person, assume it is a problem and check the authority’s page.

5. Tools and sporting goods

Tools longer than about seven inches go in a checked bag; shorter ones generally travel. Screwdrivers and wrenches are usually fine at that size, and a drill is not, whatever its length.

Sporting goods follow a simpler rule: anything that works as a club is checked. Baseball bats, golf clubs, ski poles, hockey sticks, pool cues. Small equipment — a tennis racket, boxing gloves, a yoga mat — travels in the cabin.

The myths: things you can absolutely bring

Half the value of a page like this is deleting items from your worry list.

• Nail clippers and tweezers. Both fine, and both perennially believed not to be.
• Disposable razors. Fine.
• Knitting needles. Fine.
• An empty water bottle. Fine, and the single best thing to carry — empty it before the checkpoint, refill after.
• Solid food. Sandwiches, snacks, fruit, hard cheese, a whole cake. All fine.
• Umbrellas and walking sticks. Fine, though they may be inspected.
• Laptops, cameras, drones. Fine in the cabin, and that is where they belong anyway.
• Prescription medication. Fine, in any reasonable quantity, and it does not have to be in its original packaging in the US — though the original label makes questions shorter.
• A lighter. One common lighter on your person is generally permitted; the fuel to refill it is not.

Things that are allowed but that you should still leave out

A different list: not prohibited, just a bad idea in a bag you may be asked to hand over at a gate.

• Anything irreplaceable.If a gate-check would ruin your week, it belongs in the bag that never leaves you — which is your personal item, not your carry-on.
• Full-size toiletries you will not use. Weight you carry for ten days to use twice.
• A second charger. One charger, one bank, the right cables. The rest is a pouch full of hedging.
• Wrapped gifts. Not banned, but a screener may need to open them, and then they are unwrapped gifts.

A two-minute check before you leave home

• Empty every pocket of the bag, including the ones you forgot it has. Multitools live there.
• Liquids in one quart bag, nothing over 100 ml, bag reachable without unpacking.
• Power bank and spare batteries in the cabin bag; nothing loose against keys or coins.
• Water bottle empty.
• If in doubt about a specific item, check the issuing agency’s own current page — not a listing, a forum or a page like this one from a year ago.

Pair this with the size guide and you have covered both halves of the problem: what can go in the bag, and how big the bag is allowed to be.