What does the TSA 3-1-1 rule actually mean?

The 3-1-1 rule means each liquid, gel, aerosol, cream, or paste in your carry-on must be in a container of 3.4 ounces (100 ml) or less, all containers must fit in 1 quart-size clear zip-top bag, and each traveler is allowed 1 bag. Anything larger gets confiscated — even if the container is not full.

Is it 3.4 oz or 100 ml — which is correct?

Both are correct. TSA rounds 100 ml up to 3.4 fluid ounces for U.S. labeling, but the actual legal limit is 100 ml. If your container says '100 ml' or '3.4 fl oz' and no more, you are compliant. A '3.5 oz' or '4 oz' bottle is not compliant even if it is only half-full.

What are the most commonly confiscated liquids at TSA?

The top items TSA confiscates are oversized water bottles, full-size shampoo, full-size sunscreen (especially for beach trips), peanut butter (yes, it counts as a liquid), yogurt, snow globes over 3.4 oz, hummus, honey, salsa, and opened perfume bottles over 100 ml. The rule covers anything you could pour, squeeze, spread, or spray.

Can I bring medication over 100 ml?

Yes. Prescription and over-the-counter liquid medications are exempt from the 3-1-1 rule in 'reasonable quantities' for the duration of your trip. Declare them at the checkpoint, keep them separate from your quart bag, and expect extra screening. The same exemption applies to breast milk, formula, juice for infants, and medically necessary gels.

Do CT scanners let me skip the quart bag in 2026?

At some U.S. airports, yes. TSA's new Analogic and Smiths Detection CT scanners can screen liquids without removal from the bag, and the agency has been quietly phasing out the quart-bag requirement at retrofitted lanes. But the 100 ml per container limit has not changed — only the packaging and removal requirement. Until full national rollout (expected 2028–2030), assume the full 3-1-1 rule applies.

Is the TSA rule the same in Europe, Asia, and the UK?

The 100 ml per-container standard is globally aligned, but quart-bag and scanning rules vary. UK airports with new CT scanners have lifted the 100 ml limit to 2 liters at some lanes, but reinstated restrictions at others in 2024 after scanner issues. The EU still enforces 100 ml. Asia varies by airport. Always check the departure airport's current rule the week before you fly, not the week before you booked.

Does the 3-1-1 rule apply to duty-free liquids?

No — liquids purchased at duty-free after security are allowed in any volume, as long as they are sealed in the tamper-evident STEB (Security Tamper-Evident Bag) with the receipt visible. The catch: if you have a connecting flight and need to re-clear security, the bag must remain sealed and you may be required to show the receipt. Opening the STEB voids the exemption.

Will TSA confiscate my snow globe?

Yes, if it contains more than 3.4 oz of liquid — and most snow globes do. TSA publishes snow globes as one of their top confiscated items around the holidays. Pack them in checked luggage, or ship them home. Same rule applies to decorative bottles, perfume gift sets, and jarred preserves over 100 ml.

Air Canada Carry-On Size in Centimetres, and Why a US 22-Inch Bag Is Over

Air Canada carry-on and checked baggage size limits

Air Canada writes its carry-on rule in centimetres first: 23 x 40 x 55 cm (9 x 15.5 x 21.5 in), wheels and handles included. That 55 cm is where the trouble is for anyone flying in from the United States, because the bag American retailers sell as "the standard carry-on" is 22 inches tall, and 22 inches is 55.88 cm. It is over Air Canada's published height by just under a centimetre.

The numbers, exactly as Air Canada prints them

What Air Canada publishes	Official figure
Carry-on (inches)	21.5 × 15.5 × 9 in
Carry-on (centimetres)	55 × 40 × 23 cm
Personal item (inches)	17 × 13 × 6 in
Personal item (centimetres)	43 × 33 × 16 cm
Carry-on weight limit	No stated limit
Wheels and handles counted?	Yes
Checked bag: max weight	50 lb / 23 kg
Checked bag: max total size	62 in / 158 cm

Where these numbers come from: Air Canada carry-on page, Air Canada checked bag page. Read and recorded on 2026-08-31. Every figure on this page is copied from those pages — nothing here is estimated. Airlines change baggage rules without notice, so check the official page before you fly.

A US "standard" carry-on is 0.88 cm too tall for Air Canada

The arithmetic is not in dispute. 22 inches is 55.88 cm. Air Canada's published maximum height is 55 cm. A US-market 22-inch carry-on is over by 0.88 cm before anything is packed into it, and Air Canada states that the maximum dimensions "include wheels and handles," so there is no version of the measurement that saves it.

In practice a soft-sided bag at 55.88 cm rarely gets pulled aside. A hard-shell case at the same height, presented to a gate agent who is watching bin space run out, is a different story — it does not compress into the sizer, and it is exactly the type of bag that gets asked. If you fly Air Canada often and you are buying, look for cases sold as 21 or 21.5 inches rather than 22.

Where Air Canada is unusually generous is in the other two directions. Its width allowance is 40 cm, against 35–36 cm at American, United and Delta, and its depth is 23 cm. The resulting box holds about 50.6 litres, more than the American standard's roughly 46 and well ahead of Korean Air's 44. Short and fat beats tall and thin here.

Air Canada is also the only airline in this group that states in writing that there is no cabin weight limit — the wording is that the bag "must be light enough that you can store it in the overhead bin without assistance." That is a real allowance, not an oversight, and it is why Air Canada suits people carrying dense items such as camera bodies or books.

The personal item is generous too, at 33 x 43 x 16 cm, and Air Canada permits a small purse of up to 25 x 30 x 14 cm on top of it. It is explicit that anything larger than that purse counts against your carry-on allowance rather than being free.

Measuring your own bag against these numbers

The bag most retailers label "the standard carry-on" is 22 x 14 x 9 inches. Converted exactly, that is 55.88 x 35.56 x 22.86 cm, and the three sides add to 114.3 cm. Held against Air Canada's published limits, here is where it stands.

It does not fit — at least not on paper.

Longest side: the standard bag is 55.88 cm against a published limit of 55 cm — over by 0.88 cm.

This one is not a rounding artefact. Air Canada publishes its limits in centimetres first, and the shortfall is real enough that a rigid case will be visibly proud of a sizer. A soft bag at the same nominal size usually passes because it compresses; a hard shell often does not.

The reverse question matters just as much if you already own luggage. A bag bought to fit Korean Air also clears Air Canada. A bag bought to fit Southwest Airlines, Frontier Airlines, JetBlue, American Airlines, United Airlines, Delta Air Lines does not — those boxes are larger than Air Canada allows in at least one direction.

Whichever airline you are flying, measure the same way the airline does: bag packed, tape across the widest bulge rather than the frame, wheels and handle included, expansion zip closed. Every airline on this page that says anything about wheels says they count.

What Air Canada does not publish

These were checked against Air Canada's own baggage pages on 2026-08-31. The following are simply not stated there, so treat any number you find elsewhere for them as somebody's inference rather than a rule:

A carry-on weight limit in pounds
A combined length + width + height cap
A personal item weight limit
How many checked bags are included

Air Canada does not publish a carry-on weight limit because it does not have one — that is stated, not missing.

How Air Canada compares with the other seven

Air Canada has the largest cabin allowance of any full-service carrier here, and no weight limit at all. Air Canada ranks third of the eight by published cabin volume at 50.6 litres, between Southwest Airlines's 62.9 at the top and Korean Air's 44.0 at the bottom. Volume is the published box multiplied out, which is the fairest way to compare boxes of different shapes.

Airline	Carry-on (in)	Carry-on (cm)	Volume (L)	Weight cap	Personal item (in)
Frontier Airlines	24 × 16 × 10 in	61 × 40.6 × 25.4 cm†	62.9	35 lb	18 × 14 × 8 in
Air Canada	21.5 × 15.5 × 9 in	55 × 40 × 23 cm	50.6	None stated	17 × 13 × 6 in
American Airlines	22 × 14 × 9 in	56 × 36 × 23 cm	46.4	—	18 × 14 × 8 in

† converted from the figure the airline does publish. Southwest and Frontier publish inches only; Korean Air publishes centimetres only. Everything without a dagger is printed on the airline's own page in that unit.

The full eight-airline table, including checked bag limits, is on the comparison page. Alaska Airlines is deliberately absent from it: its baggage pages would not open to us, and we would rather leave a gap than print a figure we could not read on an official page.

Buying a bag for Air Canada

Look for cases sold as 21 or 21.5 inches, or metric cases at 55 cm or below. Air Canada's extra width — 40 cm against 35 or 36 elsewhere — means a shorter, wider case gives you more usable volume here than the tall American shape does, and it stays legal.

Weight is not your problem on Air Canada; the page says so. Bin space is. Air Canada notes that bags may be gate-checked when the cabin is full, with fees quoted for that at the gate, so boarding group matters more than grams.

The other seven airlines

Related pages on TripPack

All eight airlines in one table — carry-on, personal item and checked limits side by side.
Carry-on packing list — what to actually put in the bag once you know it fits.
How to measure a carry-on bag — where to hold the tape.
Baggage weight limits explained.