Does the 3-1-1 rule apply to checked bags?

No. The 3-1-1 rule only applies to carry-on luggage. You can pack full-size liquids, gels, and aerosols in your checked bags without size restrictions (with minor exceptions for flammable items and high-proof alcohol).

Can I bring a half-empty bottle larger than 3.4 ounces?

No. TSA goes by container size, not the amount of liquid inside. A half-empty 6-ounce bottle will be confiscated even though it contains less than 3.4 ounces of liquid. The container itself must be 3.4 ounces or smaller.

Is toothpaste considered a liquid by TSA?

Yes. Toothpaste is classified as a paste/gel and falls under the 3-1-1 rule. You'll need a travel-sized tube of 3.4 ounces or less, and it must go in your quart-sized bag. Alternatively, toothpaste tablets are solid and bypass the rule entirely.

Are medications exempt from the 3-1-1 rule?

Yes. Prescription and over-the-counter liquid medications can exceed 3.4 ounces and don't need to fit in your quart-sized bag. Declare them to the TSA officer at the checkpoint, and they'll go through additional screening.

Can I bring breast milk or baby formula through security?

Yes. Breast milk, baby formula, and juice for infants are exempt from the 3-1-1 rule and allowed in quantities greater than 3.4 ounces. You don't need to be traveling with a child to bring breast milk. Remove these items from your bag and inform the TSA officer for separate screening.

What Is the TSA 3-1-1 Rule? Liquids Explained

The Rule in Plain English

TSA's 3-1-1 rule breaks down like this:

3.4 ounces (100 ml) - Maximum size per container
1 quart-sized bag - All containers must fit inside a single clear, resealable bag
1 bag per passenger - Everyone gets exactly one liquids bag

That's it. Every liquid, gel, aerosol, cream, and paste in your carry-on needs to follow this rule. If it spreads, flows, sprays, or smears, it counts.

What Counts as a "Liquid"

TSA defines liquids more broadly than you'd think. It's not just water and shampoo. Here's what falls under the 3-1-1 rule:

Obvious liquids - Water, juice, coffee, contact lens solution, liquid makeup
Gels - Toothpaste, hair gel, lip gloss, hand sanitizer
Creams - Moisturizer, sunscreen, body lotion, ointments
Pastes - Toothpaste (yes, it's both), peanut butter, hummus
Aerosols - Hairspray, dry shampoo, travel-size deodorant spray

A good rule of thumb: if you can pour it, squeeze it, or spread it, treat it as a liquid for TSA purposes.

Container Size Matters, Not How Much Is Inside

This trips people up constantly. TSA cares about the container size, not how much liquid is actually in it. A half-empty 8-ounce bottle of shampoo will get confiscated, even though there's only 4 ounces of shampoo inside.

The container itself must be 3.4 ounces (100 ml) or smaller. Period. If it says 4 oz on the label, it's getting tossed regardless of how much is left.

The Quart-Sized Bag

Your containers need to fit inside a single quart-sized (roughly 7 x 8 inches) clear plastic bag. A standard Ziploc sandwich bag is actually a quart size and works perfectly fine.

The bag needs to be:

Clear - So TSA can see what's inside
Resealable - Zip-top closure
Quart-sized - Not gallon-sized, not snack-sized

Some brands sell reusable TSA-approved bags, which look nicer than a Ziploc but aren't required. As long as it's clear and roughly quart-sized, you're fine.

Exemptions to the 3-1-1 Rule

Not everything has to follow the 3-1-1 rule. These items are exempt and can exceed 3.4 ounces in your carry-on:

Medications

Prescription medications in liquid, gel, or aerosol form (keep them in original packaging)
Over-the-counter liquid medicines like cough syrup, pain relievers, and allergy meds
Medically necessary liquids of any size

You don't need to fit these in your quart bag, but you should declare them to the TSA officer at the checkpoint. They'll go through additional screening.

Baby and Child Items

Breast milk (in any quantity, even if you're not traveling with a child)
Baby formula
Juice for infants and toddlers
Jarred and processed baby food
Gel or liquid-filled teethers

Ice packs and freezer packs to keep formula or breast milk cold are also allowed. Remove these items from your bag and tell the TSA officer you have them. They'll be screened separately.

Other Exemptions

Saline solution and eye drops (in reasonable quantities)
Life-sustaining liquids like insulin
Duty-free liquids in sealed bags (with some airline restrictions)

What About Checked Bags?

The 3-1-1 rule only applies to carry-on luggage. In your checked bags, you can pack full-size bottles of shampoo, conditioner, lotion, and whatever else you want. There's no liquid size limit for checked luggage, though there are some restrictions on flammable aerosols and alcohol content above 140 proof.

This is why many travelers check a bag with their full-size toiletries and keep a small 3-1-1 bag in their carry-on with just the essentials.

How to Pack Your 3-1-1 Bag Like a Pro

Buy travel-size containers - Reusable silicone bottles work great and won't leak. Fill them with your preferred products
Switch to solids - Solid shampoo bars, bar soap, solid deodorant, and toothpaste tablets don't count as liquids and bypass the rule entirely
Pack the bag on top - You'll need to pull it out of your carry-on and place it in a bin at security. Don't bury it at the bottom
Skip what hotels provide - Most hotels offer shampoo, conditioner, lotion, and body wash. Save your quart bag space for things they don't provide
Check if it's really a liquid - Solid deodorant, bar soap, powder makeup, and solid perfume are all fine outside the bag

What Happens If You Break the Rule?

You won't get arrested. The TSA officer will simply confiscate the item that doesn't comply. If your shampoo bottle is 4 ounces instead of 3.4, they'll toss it in the bin. You can either surrender it or step out of the security line, check it in your luggage, and go through screening again.

There's no fine or penalty. It's just inconvenient and wasteful. Better to pack right the first time.

The Screening Process

At the TSA checkpoint, you'll need to remove your quart-sized bag from your carry-on and place it in a separate bin for X-ray screening. This applies at standard screening lanes. If you have TSA PreCheck, you can typically leave your liquids bag inside your carry-on.

If the X-ray operator sees something questionable, they'll pull your bag for a manual inspection. This usually takes less than a minute.