TSA Liquid Rules: The 3-1-1 Limit Explained

TSA's own wording is direct: each passenger can carry liquids, gels and aerosols in travel-size containers of 3.4 ounces (100 ml) or less per item, and all of those containers have to fit inside a single quart-size, clear, zip-top plastic bag. One bag per traveler. If your container is 3.4 ounces or under but the bottle itself is larger (like a mostly-empty 8 oz shampoo bottle), it still gets flagged, because TSA reads the container size printed on the bottle, not how much liquid is actually left inside.

This covers the obvious stuff: shampoo, conditioner, toothpaste, mouthwash, lotion, sunscreen, contact lens solution, and most drinks. It also covers less obvious items people forget are liquids under TSA's definition, including peanut butter, yogurt, salad dressing, and any gel-based item like hair gel or gel deodorant. If it pours, spreads, sprays, or can be spilled, TSA treats it as a liquid for screening purposes.

The quart bag itself has to be clear so the screener can see the contents without opening it. Ziploc-style bags work fine; TSA doesn't sell or require a specific brand. You're allowed to pack more liquid in your checked bag with no 3.4 oz cap at all, since the 3-1-1 rule only governs what goes through the carry-on checkpoint.

A handful of items are exempt from the 3.4 oz cap and don't need to fit in the quart bag, though they still have to be declared to the screener and screened separately. Breast milk, baby formula, and juice for an infant or toddler are allowed in quantities greater than 3.4 ounces, per TSA's own guidance, and you don't need to be traveling with the child for this exception to apply.

Medically necessary liquids, including prescription medication, over-the-counter medication, and liquid nutrition, are also allowed above 3.4 ounces. Tell the officer you're carrying medically necessary liquids before screening begins and keep them accessible; TSA may test them separately from your other bags.

None of these exceptions change your airline's separate carry-on bag size limit. A bag full of formula or medication still has to physically fit in whatever carry-on or personal item dimensions your airline enforces, which is a completely different set of numbers than anything TSA publishes.

TSA PreCheck doesn't remove the 3.4 oz liquid cap, but it usually removes the hassle around it. PreCheck travelers typically keep laptops and 3-1-1 liquids inside their bag during screening, along with keeping shoes on and belts fastened, instead of pulling everything out into a bin. The container size limit and quart-bag rule are identical for PreCheck and standard screening; the only thing that changes is whether you have to unpack your bag to prove it.

If a PreCheck lane isn't open at your airport, you can usually still keep your PreCheck boarding pass and get some of these conveniences in the standard lane, but this varies by checkpoint, so don't assume it's guaranteed at every airport on every trip.

This is where two separate systems collide and travelers assume they've been cleared twice when they've really only been cleared once. TSA checks what's inside your bag for security purposes: sharp objects, liquids over 3.4 oz, prohibited items. Nothing about that screening measures whether your suitcase fits in an overhead bin.

Your airline enforces a completely separate size limit, and it varies by carrier. Most U.S. airlines cap a standard carry-on around 22 x 14 x 9 inches (45 linear inches when you add the three dimensions together), but some allow more: Frontier and Southwest both publish a 50-linear-inch limit, and British Airways allows 56 x 45 x 25 cm (about 50 linear inches) on its cabin bag. A bag that sailed through the TSA checkpoint can still get flagged by a gate agent's sizer box if it's oversized for that specific airline, and at that point you're paying a gate-check or bag fee that has nothing to do with security.

The fix is to check both rules before you fly: TSA's liquid limit for what's inside your bag, and your specific airline's carry-on dimensions for the bag itself. You can run your exact bag against every major carrier's limits with the free fit checker on this site instead of guessing.

Buy travel-size versions of your usual toiletries rather than trying to decant full-size bottles at the last minute; pre-measured 3 oz or 100 ml bottles avoid the guesswork and the risk of a screener flagging an unlabeled container. Solid alternatives dodge the rule entirely: solid deodorant, shampoo bars, and solid perfume sticks aren't liquids, gels, or aerosols, so they don't count against your quart bag at all.

If you're checking a bag on your trip anyway, it's often simpler to pack full-size toiletries in the checked bag and keep only the essentials you need mid-flight in your quart bag. That said, checked bags come with their own weight and size limits and, on budget carriers especially, a real fee, so it's worth comparing the cost of checking a bag against just buying travel sizes for a short trip.