TSA Liquid Rule: How Many Ounces Can You Bring on a Plane?

TSA calls its carry-on limit the 3-1-1 liquids rule. The name matches its three limits: containers of 3.4 fl oz or less, one quart-size bag, and one bag per passenger.

The rule covers liquids, gels and aerosols, so toiletries such as toothpaste and shampoo count too. The bag is named after the US quart, which is 32 fl oz, or about 946 ml.

Your travel bottles all have to fit inside that one bag. Their shape matters as much as their size, so pack flat or slim bottles when you can.

Almost. 100 ml is 3.381 fl oz, which rounds to the 3.4 fl oz that TSA prints. Going the other way, a full 3.4 fl oz is 100.6 ml.

TSA gives both numbers side by side, so a travel bottle labeled either way meets the limit as written. In UK (imperial) fluid ounces, the same 100 ml is 3.52 imp fl oz. To check other sizes, use the ounces to milliliters converter.

TSA makes exceptions for three kinds of liquids:

• Medicine. Medically necessary liquids, gels and aerosols are allowed in larger, reasonable amounts for your flight, but you must declare them.
• Baby and toddler items. Formula, breast milk, toddler drinks and baby food, including puree pouches, are allowed in amounts over 3.4 fl oz. They do not have to fit in the quart-size bag.
• Duty-free liquids. Larger duty-free liquids can ride in your carry-on in a sealed, tamper-evident bag if you bought them within the last 48 hours, keep the receipt, and are flying into the US from abroad with a connecting flight.

The basic limit uses the same metric size. GOV.UK says most UK airports only allow liquids in containers of 100 ml or less, packed in one clear, resealable bag that holds no more than 1 liter. Some UK airports may allow containers of up to 2 liters, so check with your airport before you fly.

At all UK airports, liquids for medical needs, special diets, and baby food or baby milk can come in containers of up to 2 liters.

For the EU, Your Europe gives the same basic rule: no container over 100 ml, carried in a clear plastic bag of up to 1 liter. A US quart is a little less than a liter, so the bags on both sides of the Atlantic are close in size.

TSA says to pack anything in a container larger than 3.4 fl oz in your checked baggage. That is the simple fix for a full-size bottle of shampoo or lotion.

Alcohol has its own limits. Drinks with 24% alcohol or less have no TSA limit in checked bags, while stronger drinks, up to 70% alcohol, are limited to 5 liters (1.3 gallons) per passenger in unopened retail packaging.