TSA Liquid Rules, Airline Size Limits, and Other Carry-On Facts Worth Knowing

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

The TSA's 3-1-1 rule governs how liquids, gels, aerosols, creams, and pastes may be packed in carry-on bags on flights departing from U.S. airports. Here's how it breaks down:

• 3.4 oz (100 ml) or less per container — individual containers must not exceed this volume regardless of how full they are.
• 1 quart-sized, clear zip-top bag — all liquid containers must fit inside a single bag of this size.
• 1 bag per passenger — each traveler is allowed one such bag, which must be removed from the carry-on and placed in the screening bin.

Items like toothpaste, shampoo, conditioner, lotion, liquid foundation, and even peanut butter fall under this rule. Solid alternatives — bar soap, solid shampoo, and stick deodorant — are not subject to the liquid limit and can simplify packing considerably.

Exceptions apply to medications, baby formula, and breast milk, which are permitted in quantities exceeding 3.4 oz. Travelers carrying these items should declare them at the checkpoint and be prepared for additional screening.

For a broader look at how carry-on strategy fits into your overall packing approach, see Packing Light vs. Checking Bags for a full trade-off breakdown.

Standard U.S. Airline Carry-On Size Limits

Carry-on size limits are set by individual airlines, not the TSA — so dimensions can vary. That said, most major U.S. carriers cluster around a common range. Always verify with your specific airline before travel, since policies can change and enforcement varies by aircraft and route.

A few things worth noting about size limits in practice:

• Overhead bin space is first-come, first-served. Boarding later in your group often means your bag ends up gate-checked.
• Soft-sided bags have flex advantage. A bag that's slightly oversized may still fit if it compresses; hard-sided shells have zero give.
• Personal items go under the seat. Most airlines allow a personal item (purse, backpack, laptop bag) in addition to a standard carry-on. Size limits for personal items are typically around 18" x 14" x 8", but again, check your carrier.

If you're deciding between carry-on only and a checked bag for your next trip, Carry-On vs. Checked Bag: Picking the Right Strategy walks through the key considerations by trip type.

What's Not Allowed in Carry-Ons

Beyond liquids over 3.4 oz, a range of items are restricted or outright prohibited in carry-on bags. The TSA maintains a full list on its website (the TSA's "What Can I Bring?" tool is searchable by item), but the most commonly misunderstood categories include:

• Sharp objects: Box cutters, straight razors, and knives with blades longer than 4 inches are prohibited. Disposable razors and safety razors (blade removed) are allowed.
• Firearms and ammunition: These must be transported unloaded in a hard-sided, locked container in checked baggage only, with proper airline notification.
• Lithium batteries: Spare lithium-ion batteries and power banks must travel in carry-on bags — not checked luggage — due to fire risk. Devices with installed batteries may go either way.
• Tools over 7 inches: Wrenches, pliers, and similar tools exceeding 7 inches in length are prohibited in carry-ons.
• Flammable liquids and gels: Lighter fluid, spray paint, and similar items are not permitted in either carry-on or checked bags.

When in doubt, the TSA's online tool gives real-time guidance. International flights may carry additional restrictions layered on by the destination country's regulations — always verify entry requirements through official government sources before departure.

Use Your Pre-Trip Packing Checklist for Domestic Flights to make sure nothing gets left behind — or accidentally packed in the wrong bag.

Quick Reference: Carry-On Rules at a Glance

Packing smart starts with knowing the rules cold. The most common airport security delays stem from liquid violations and prohibited items that could have been left at home or transferred to checked luggage. A few habits that help:

• Pack your quart-sized liquid bag at the top of your carry-on for easy retrieval at security.
• Keep electronics (laptops, tablets) accessible — they typically need to be removed and screened separately.
• If you're traveling internationally, review the destination country's customs rules in addition to TSA guidelines. International Travel Packing: Documents, Adapters, and Forgotten Essentials covers the items most travelers overlook.
• Challenge your packing assumptions — Travel Gear Myths That Keep Travelers Overpacking debunks several common beliefs that lead to overstuffed bags.

TSA rules are subject to update. Always verify current guidelines at tsa.gov and with your airline before your travel date.