TSA Liquid Rules for Carry-On Bags
The Transportation Security Administration requires passengers to follow the 3-1-1 rule for liquids in carry-on luggage. Each container must hold 3.4 ounces or 100 milliliters or less, and all containers must fit inside one clear, quart-sized, resealable plastic bag. This rule applies to water, beverages, gels, aerosols, creams, and pastes. The bag must be placed in a bin for X-ray screening at the security checkpoint. For the official current policy, see the TSA's official page on liquids and gels TSA liquids and gels rules.
Exceptions to the 3-1-1 rule include medically necessary liquids, baby formula, breast milk, and juice for infants. These items may exceed the size limit but must be declared at the checkpoint and may undergo additional screening. Prescription medications and over-the-counter liquids in reasonable quantities for the trip are also exempt from the 3-1-1 rule, though they may be subject to additional inspection. You do not need to place these items in the quart bag, but keeping them separate can speed up screening.
Why TSA Checks Liquids and Exceptions for Duty-Free
The liquid ban was introduced in August 2006 after intelligence reports revealed a plot to detonate explosives on transatlantic flights using liquids. The rule aims to limit the volume of potential explosive precursors a passenger can carry in the cabin. The TSA periodically reviews these rules and updates procedures based on threat assessments and operational experience. For background on the security rationale, see the TSA's security overview TSA security screening overview.
Duty-free liquids purchased in a secure international transit area may be carried in carry-on bags if they are sealed in a tamper-evident bag and you have the receipt. The exemption applies only if the purchase was made after the security checkpoint and the bag remains intact. If you are connecting to another flight, the rules for duty-free liquids depend on the regulations of your final destination and any intermediate airports. For more on international variations, see the U.S. Customs and Border Protection guidance CBP duty-free information.
Packing Liquids for TSA and Checking Bag Options
To streamline screening, pack your quart-sized bag of liquids at the top of your carry-on and be prepared to remove it separately. Use travel-sized containers that clearly show the volume, and avoid overfilling them. Laptops, large electronics, and liquids bags should be placed in bins according to TSA officer instructions at the checkpoint. For guidance on packing efficiently, see TSA's travel tips TSA travel tips.
If you prefer not to deal with liquid restrictions, you can pack all liquids in checked baggage. Checked bags do not have the 3.4-ounce container limit, but aerosol cans must be marked with a proper classification and limited to 18 ounces each. Airlines and the TSA recommend securing liquid containers to prevent leakage and damage. For details on what is allowed in checked bags, see the TSA's checked baggage page TSA checked baggage liquid rules.