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01Check your power bank
The checker turns milliamp-hours into watt-hours, the unit airlines and the TSA actually use, and gives you a verdict against the 100 Wh and 160 Wh lines. It only answers one question: is this battery a legal size? Packing rules, the two-bank limit and in-flight use are covered in our full guide to power bank rules on planes.
02Find the right numbers on the label
Flip the bank over. The fine print on the back or side usually has everything you need, though it's often molded into the plastic in tiny gray text. A phone flashlight held at an angle helps.
| What the label says | What it means | Use it? |
|---|---|---|
| "37Wh" or "Energy: 74Wh" | The watt-hour rating, already calculated | Yes. This is the number security wants |
| "Capacity: 10000mAh 3.7V" or "3.6V" | Cell capacity and cell voltage | Yes. Put both into the checker |
| "Rated capacity: 6000mAh (5V 2.4A)" | What reaches the USB port after conversion | No. Use the cell capacity instead |
| "Input 5V/3A, 9V/2A" | How fast the bank recharges | No. Unrelated to the airline limit |
| "Output 20W" or "PD 22.5W" | Maximum charging power for your phone | No. Also unrelated |
03Why rated capacity gives the wrong answer
Many banks print two mAh figures. The big one on the box is the cell capacity, measured at the cells' own voltage (3.6 to 3.7V). The smaller "rated capacity" is what's left after the bank boosts that to 5V for USB, minus conversion losses. Airlines care about the energy stored in the cells, so the cell figure is the one to use.
Wh = cell mAh × cell voltage ÷ 1,000A bank labeled 26,800 mAh at 3.7V works out to 99.2 Wh: legal, but with almost no margin.
If you plug the rated capacity and 5V into the checker, the result can look higher or lower than reality depending on how efficient the bank is. Stick to the pair printed together, cell mAh and cell voltage, and you'll match what an airport agent works out.
04GripLux power banks, checked
Here's what our current banks come to at a 3.7V cell voltage, based on the capacity in each product name. Always confirm against the label on the bank you receive.
| Power bank | Capacity | Approx. Wh | Verdict |
|---|---|---|---|
| Lipstick-Size Mini | 2,600 mAh | 9.6 Wh | Carry-on OK |
| Pocket Magnetic Wireless | 5,000 mAh | 18.5 Wh | Carry-on OK |
| Slim MagSafe-Compatible Wireless | 8,400 mAh | 31.1 Wh | Carry-on OK |
| Compact with Display | 10,000 mAh | 37 Wh | Carry-on OK |
| Ultra-Thin Aluminum | 12,000 mAh | 44.4 Wh | Carry-on OK |
| Everyday Portable | 20,000 mAh | 74 Wh | Carry-on OK |
| 30,000 mAh with LCD Display | 30,000 mAh | 111 Wh | Over 100 Wh. Leave it home for flights |
| High-Capacity, 20,000–50,000 mAh | Depends on version | 74–185 Wh | Only the 20,000 mAh version is flight-friendly |
Honest advice: if you fly more than once or twice a year, don't buy a 30,000 mAh bank as your only one. Pair a 20,000 mAh bank for trips with a bigger one that stays home for camping and power cuts.
Sizes that clear airport security without a second look.
05When the checker can't settle it
- No label, or it's worn off. Security staff can refuse a battery they can't identify. Find the product page or manual and screenshot the specs, or leave it behind.
- Battery cases and magnetic battery packs. They count as power banks, so check them the same way.
- Two banks in one bag. Each is checked on its own Wh, but the 2026 global rules cap you at two power banks per person.
- A bank close to 100 Wh. Anything from about 95 Wh up is legal but invites questions. Make sure the Wh figure is printed on it.
Not sure which size to buy in the first place? Our guide on how to choose a power bank weighs capacity against weight, and the power bank charge calculator shows how many phone charges each size gives you.
Questions people ask
How do I convert mAh to Wh for a power bank?
Multiply the mAh by the cell voltage and divide by 1,000. Most power banks use 3.6 or 3.7V cells, so a 10,000 mAh bank is about 37 Wh and a 20,000 mAh bank about 74 Wh.
What is the largest mAh power bank allowed on a plane?
About 27,000 mAh at 3.7V, which is just under 100 Wh. Banks up to that size can go in your carry-on on any airline. Bigger ones need airline approval at best and are often refused.
Which voltage should I use, 3.7V or 5V?
Use the cell voltage printed next to the main mAh figure, usually 3.6V or 3.7V. The 5V figure describes the USB output, and pairing it with the cell mAh overstates the battery's energy.
What if my power bank doesn't show mAh or Wh?
Look up the model's product page or manual and keep a screenshot with you. Airport staff can refuse a battery whose rating they can't confirm, so an unlabeled bank is a gamble.
Is a 30,000 mAh power bank OK to fly with?
Usually not. At 3.7V it's around 111 Wh, over the 100 Wh limit. Some airlines may approve it on request, but many follow the 2026 global guidance and won't. A 20,000 mAh bank is the safer travel size.