Why airlines use Wh instead of mAh
The number printed largest on a power bank is almost always mAh, but the rules are written in watt-hours. That's because mAh describes charge alone and ignores voltage — two packs with identical mAh can hold different amounts of energy depending on how their cells are arranged. Fire risk tracks total energy, so the regulation tracks watt-hours.
The conversion is straightforward: Wh = mAh × V ÷ 1000. With the usual 3.7 V lithium-ion nominal voltage, a 20,000 mAh pack is about 74 Wh. Where a manufacturer prints the Wh rating directly, use that figure — it accounts for the actual internal configuration rather than an assumed voltage.
The three thresholds
Under the dangerous goods framework most carriers follow, spare lithium batteries up to 100 Wh can be carried on without any special permission. That covers the overwhelming majority of consumer power banks — 100 Wh is roughly 27,000 mAh at 3.7 V, which is larger than most people travel with.
Between 100 and 160 Wh you move into approval territory: you need your airline's consent in advance, and you're typically limited to two spares. Above 160 Wh the answer is simply no — not in the cabin, not in the hold. Large camping and portable-power-station units usually land here, and they need to be shipped as cargo instead.
The mistakes that actually cause problems
Far and away the most common is packing a power bank in a checked bag. It's easy to forget one zipped into a laptop sleeve or a suitcase pocket, and screening will find it. Do a deliberate check before you hand anything over at the desk.
The second is an unreadable label. If the capacity marking has worn off and there's no Wh or mAh figure to verify, staff can refuse the item because they have no way to confirm it's within limits. Travel with units whose markings are still legible, and tape the terminals or bag each one separately so nothing can short against keys or coins.
What this calculator assumes
- Wh = mAh × V ÷ 1000, with a 3.7 V default (lithium-ion nominal)
- Up to 100 Wh: carry-on without approval · 100–160 Wh: airline approval, usually max two
- Over 160 Wh: not permitted in cabin or checked baggage
- Spare batteries and power banks are cabin-only everywhere
- Primary sources: IATA guidance for passengers travelling with lithium batteries (PDF) · FAA PackSafe — Lithium Batteries
This page is general guidance, not an official ruling. Requirements differ by carrier and country and have been tightening — confirm with your airline before departure.
Frequently asked questions
How do I convert mAh to Wh?
Wh = mAh × voltage (V) ÷ 1000. Lithium-ion cells are usually rated at 3.7 V nominal, so a 20,000 mAh power bank works out to 20000 × 3.7 ÷ 1000 = 74 Wh. If the Wh figure is printed on the unit or in its manual, use that instead — it's authoritative, since internal cell arrangements can change the effective voltage.
What are the Wh limits?
Under the widely adopted IATA dangerous goods rules, spare batteries up to 100 Wh can be carried on without airline approval. Between 100 Wh and 160 Wh you need the operator's approval and are typically limited to two spares. Anything above 160 Wh is not permitted in passenger baggage at all. At 3.7 V, 100 Wh is roughly 27,000 mAh and 160 Wh roughly 43,000 mAh.
Can I put a power bank in checked baggage?
No. Spare lithium batteries and power banks must travel in the cabin, never in checked bags. A fire in the hold is much harder to detect and suppress than one in the cabin, which is why the ban is close to universal. Remember to pull them out of any bag you're checking.
How many can I bring?
For units at or under 100 Wh, most airlines allow a reasonable personal quantity, while 100–160 Wh units are usually capped at two with prior approval. Some countries and carriers are stricter — both South Korea and Japan moved in April 2026 to a maximum of two power banks per passenger regardless of capacity. Always check your specific airline before you fly.
Can I use or charge it during the flight?
That depends on the airline, and several carriers have restricted it after in-cabin battery fires. A growing number now ban using or charging power banks in flight and require them to be kept on your person or in the seat pocket rather than the overhead bin, so any problem is spotted immediately.