Travel Liquid Rules: Understanding the 3.4 oz (100ml) TSA Limit
You're at airport security. The TSA agent holds up your full-size shampoo and shakes their head. "Over 3.4 ounces," they say, tossing your $25 bottle into the bin. We've all been there. Let's decode the TSA liquid rules so it never happens again.
The 3-1-1 Rule: What It Actually Means
Maximum size per container
Clear, plastic, zip-top (≈ 20cm × 20cm)
Must fit in a single bag
This rule applies to all liquids, gels, aerosols, creams, and pastes in carry-on luggage. It's been in effect since 2006, following security concerns about liquid explosives. Whether you're flying domestically or internationally, this rule is nearly universal.
Breaking Down 3.4 oz and 100ml
In US Terms
In Metric Terms
Why the Weird Number?
The limit is actually 100 milliliters (metric). When converted to US fluid ounces, 100ml = 3.38 fl oz, which TSA rounds to 3.4 oz. So bottles labeled "3.4 oz" or "100ml" both meet the requirement.
Fun fact: Most travel-size toiletries you buy are exactly 3.0 oz (89ml) to stay safely under the limit.
What Counts as a "Liquid"? (More Than You Think)
Subject to 3-1-1 Rule
Exempt or Not Restricted
Note: Medications and baby items are exempt but must be declared at security checkpoint.
The "Spreadable Test"
TSA's rule of thumb: If you can spread it, spray it, pump it, pour it, or squeeze it, it's a liquid. Even if it seems solid (like stick deodorant with gel), if it has any liquid-like properties, it might be restricted. When in doubt, pack it in your checked bag.
Common TSA Liquid Scenarios (And How to Handle Them)
😰 "My bottle says 200ml but it's only half full"
Verdict: Not allowed. TSA looks at the container size, not how much liquid is in it. A half-empty 200ml bottle is still over the limit.
🛍️ "I bought duty-free perfume at the airport shop"
Verdict: Allowed! Duty-free liquids purchased after security screening are exempt from the 3-1-1 rule, even if over 100ml. Keep them in the sealed bag.
💊 "I need to bring liquid medication"
Verdict: Allowed in reasonable quantities. Declare it at security, keep it separate from your 3-1-1 bag. Prescription label recommended but not required.
🍷 "Can I bring a mini wine bottle?"
Verdict: Yes, IF it's ≤100ml (most mini bottles are 187ml—too big). But you can't drink it on the plane; that's against FAA rules.
🧴 "I forgot and brought full-size toiletries"
Verdict: Confiscated. You can either go back to check-in and check them, mail them home (some airports have shipping services), or surrender them. Expensive lesson learned.
Pro Traveler Tips for Liquid Compliance
🎒Use Solid Alternatives
Solid shampoo bars, solid deodorant, and bar soap aren't subject to liquid limits. They're also lighter and won't leak in your bag.
🏨Buy at Your Destination
For longer trips, buy full-size toiletries when you arrive. Grocery stores worldwide sell shampoo. No need to stretch your 100ml over two weeks.
📦Reusable Travel Bottles
Invest in a set of TSA-approved refillable bottles (usually 3 oz/89ml). Transfer from your full-size products at home. Label them clearly.
✈️Pack Smart
Keep your quart bag at the top of your carry-on, easy to remove. Many airports require you to place it in a separate bin during screening. Having it ready speeds things up.
🧪Contact Lens Solution Hack
Need more than 100ml of solution? Buy small bottles but declare medical need. Or check your main supply and carry only 1-2 days' worth in your 3-1-1 bag.
International Variations: It's Not Just TSA
Good news: Most countries follow similar rules. The 100ml limit is standard across the EU, UK, Canada, Australia, and most major airports worldwide. But there are nuances:
When in Doubt, Check
Some countries have stricter rules. Middle Eastern airports may have additional restrictions. Always check your airline's website and departure country's security requirements before you fly.
Knowledge is Your Best Travel Companion
The TSA 3.4 oz (100ml) rule isn't going away anytime soon. But now you know exactly what it means, what counts as a liquid, and how to pack smart. No more surprise confiscations at security.
Remember: 3.4 oz = 100ml. One quart bag per person. Keep it accessible. You've got this.