The Carry-On Essentials Guide: Liquids, Power Banks, and What to Actually Pack

Why Carry-On Rules Trip Up Even Experienced Travelers

You can be a seasoned traveler and still get pulled aside at security because a 120ml sunscreen slipped into your bag, or watch a gate agent flag your power bank at boarding. Carry-on rules feel simple until you're standing in line, holding up the queue, watching a favorite item head for the bin.

The good news: the core rules haven't changed much in years, and once you understand the logic behind them, packing a compliant bag becomes automatic. This guide walks through the three areas that cause the most trouble — liquids, batteries, and space — plus a practical list of the cabin items that genuinely earn their place on a long flight.

Rules vary slightly by country and airline, so always confirm with your specific carrier before you fly. But the numbers below reflect the widely adopted international standards you'll encounter across most major airports.

The 100ml Liquid Rule, Decoded

The liquids rule is the single most misunderstood part of security. Here's the version that actually keeps you moving:

• Each container must be 100ml (3.4oz) or less. It's the container size that matters, not how much liquid is inside. A half-empty 200ml bottle still fails — the label reads 200ml, so it's rejected.
• All containers go in one transparent, resealable bag, roughly 1 liter / 20cm x 20cm. One bag per passenger.
• The bag comes out at the checkpoint and goes in its own tray, separate from your other belongings.

What counts as a "liquid"

More than you'd expect. Beyond the obvious water and shampoo, security treats these as liquids: toothpaste, sunscreen, deodorant sticks that are gel-based, lip balm in pot form, mascara, yogurt, jam, honey, and even soft cheese. When in doubt, if you can spread it, squeeze it, or pour it, assume it's a liquid.

The exceptions worth knowing

• Medication in liquid form is generally allowed over 100ml when medically necessary — declare it separately at the checkpoint, and carry a prescription or doctor's note if you can.
• Baby formula, breast milk, and baby food are exempt in reasonable quantities when traveling with an infant.
• Duty-free liquids bought after security are fine, provided they stay sealed in the tamper-evident bag with the receipt visible, especially if you have a connecting flight.

Power Banks and Batteries: The Rules That Catch People Out

Lithium batteries are the fastest-growing source of carry-on confusion, largely because the rules run opposite to what most people assume. Here's the key reversal:

Power banks and spare lithium batteries must go in your carry-on, never in checked luggage. The reason is safety — a battery fire in the cabin can be spotted and dealt with immediately, whereas one in the cargo hold cannot. So the item you might instinctively toss in your suitcase is exactly the one that has to stay with you.

The watt-hour (Wh) limits

Airlines rate power banks by capacity in watt-hours, not the mAh number printed on the front. The common thresholds:

• Up to 100Wh: generally allowed without special approval. This covers the vast majority of consumer power banks — a typical 20,000mAh unit is around 74Wh.
• 100Wh to 160Wh: usually allowed but often requires airline approval, and you're typically limited to two.
• Over 160Wh: generally prohibited in the cabin altogether.

To convert mAh to Wh: multiply the mAh by the voltage (usually 3.7V for lithium cells), then divide by 1,000. A 26,800mAh bank works out to about 99Wh — right at the edge, so check the printed rating before you pack it.

Sizing and Weight: Making Your Bag Actually Fit

The dimensions on a boarding pass are only half the story. The other half is how airlines enforce them.

• Standard cabin bag size hovers around 55cm x 40cm x 20cm, but budget carriers are stricter and often smaller. A bag that flies free on one airline may cost you a fee on the next.
• Weight limits range widely — some carriers allow 7kg, others 10kg, and a few premium cabins are more generous. Full-service airlines often don't weigh cabin bags at all, while low-cost carriers weigh them at the gate.
• The personal item (a small backpack or laptop bag that fits under the seat) is your friend. Load your heaviest, densest items here since it's rarely weighed.

A practical habit: pack, then lift your bag with one arm and hold it out. If you can't hold it comfortably for ten seconds, it's too heavy to wrestle into an overhead bin — and probably over the limit.

The Long-Haul Cabin Kit: Items That Earn Their Space

Space in a carry-on is precious, so every item should justify itself. After enough long flights, these are the ones frequent flyers keep reaching for:

• A refillable water bottle (empty through security). Fill it at a fountain past the checkpoint. Cabin air is desert-dry, and flight attendants can't top you up as often as you'd like.
• Noise-cancelling earbuds or headphones. The single biggest upgrade to sleep quality on a plane. Engine drone is exhausting even when you don't consciously notice it.
• A proper neck pillow and eye mask. Cheap ones collapse; a supportive pillow is the difference between arriving wrecked and arriving functional.
• Compression socks for flights over six hours. They genuinely reduce swelling and the risk of clots on long-haul routes.
• A small refresh kit: toothbrush, travel toothpaste (under 100ml, in your liquids bag), lip balm, and a moisturizer. Landing feeling human is worth the few grams.
• Snacks you actually like. Airline meal timing rarely matches your hunger. Nuts, dried fruit, or a protein bar bridge the gap.
• A change of underwear and a spare shirt. If your checked bag goes missing, this small insurance policy pays off enormously.

What to leave out

Full-size toiletries you'll only use at the destination, more than one "just in case" book, and duplicate chargers all add weight without adding value. If you haven't reached for it on your last three flights, it probably doesn't belong in the cabin.

Put It All Together Before You Leave Home

The travelers who breeze through security aren't lucky — they've simply built a repeatable routine. Decant liquids into 100ml bottles the week before. Keep power banks in a dedicated pouch that lives in your carry-on. Lay everything out the night before rather than packing in a pre-dawn rush.

This is where planning your trip end-to-end pays off. When you map your itinerary in myTravel, you already know your flight times, layover lengths, and how long each leg runs — which tells you exactly how much charging capacity and how many cabin comforts you actually need. A six-hour hop and a fourteen-hour marathon call for very different bags.

Confirm the specifics with your airline, respect the 100ml and power-bank rules, and pack only what earns its place. Do that, and the checkpoint becomes a formality instead of a gamble.