What Size Power Bank Do I Need for a Long-Haul Flight?

If your airline allows a power bank in flight, size it by what you charge in the air: a phone alone just barely gets by on 10,000mAh. Adding a Nintendo Switch 2 raises it to 20,000mAh and adding an iPad Air 11-inch to 25,000mAh, both just barely. A phone plus half a MacBook Air 13-inch charge needs 25,000mAh.

Power bank size for a long-haul flight at a glance

For in-flight charging, the table recommends 10,000-25,000mAh depending on your devices.

Both columns assume 0.6 efficiency. In flight counts one full charge per device, half for a laptop. After landing counts one phone charge and half a charge for the rest.

“Just barely” means the spare capacity is under a tenth of what you can use. The phone is an iPhone 18 Pro Max, with a battery size reported from EU labels. The US model hasn’t been checked.

Assuming 60% efficiency and, on a layover or after landing, one full phone charge (half for other devices), a 15-inch MacBook Air can need more than 25,000mAh. With the largest phone it needs about 54.1Wh, and 25,000mAh gives about 54Wh.

If you fly a Japanese airline

Under Japan’s rules since April 24, 2026, on Japanese airlines you may not charge a bank or charge a device from one on board. You may carry up to 2 banks of 160Wh or less, none in checked baggage. Application to foreign airlines has not been checked.

Under Japan’s rules since July 8, 2025, power banks stay out of the overhead bin on Japanese airlines; keep them where you can see them. The overhead-bin rule of US airlines has not been checked.

Charging from seat power in flight

Per American Airlines as of October 2026, American says most of its planes have AC or USB power at each seat. If yours does, try charging from the seat in flight and keep the bank for after landing. Not every plane has it, and the seat’s output and its fit with your devices have not been checked, so do not count on it.

How many Wh you can carry on

Under FAA rules, power banks of 100Wh or less can be carried on without airline approval. Those of 101 to 160Wh need the airline’s approval, and none can go in checked baggage. 20,000mAh is about 77Wh even at 3.85V, and 25,000mAh about 96Wh, both inside the 100Wh limit.

The Anker A1695 picked below (25,000mAh) is listed at 90Wh, under 100Wh. That is the 3.6V conversion, and at 3.85V it comes to about 96Wh.

100Wh is about 25,974-27,777mAh and 160Wh about 41,558-44,444mAh. 25,000mAh stays under 100Wh.

Southwest allows only 1 power bank per person. Airlines may set stricter limits than the FAA, so check your airline’s rules.

Why a power bank charges less than its label says

The label shows the battery inside the bank, and some power is lost while charging.

Per the makers’ figures, Wh is mAh × voltage ÷ 1000, so 10,000mAh at 3.7V is 37Wh.

Allowing for the power lost in charging (60-70% efficiency), a 10,000mAh bank holds 37Wh, and about 22-26Wh of it reaches your device. The makers’ figure of about 6,000-7,000mAh counts at USB’s 5V, while this article assumes more loss.

How to check your own devices

1. Find each device’s battery capacity. If it’s listed in Wh, use that. If it’s only in mAh, convert it to Wh in the next step.
2. Multiply mAh × voltage ÷ 1000 to get Wh. The voltage wasn’t found in the official specs, so use 3.85V for a device battery.
3. Multiply each device’s Wh by the number of charges you want from the bank, and add them up.
4. Multiply the bank’s Wh by 0.6 (this article’s assumed efficiency) to estimate the usable energy. Compare that with your total.
5. To pick a size, divide your total Wh by 0.6 and by 3.6V, then multiply by 1000 to get mAh. Pick that or more. Example: charging an iPhone 18 Pro Max once from 0% to 100% takes about 20.8Wh, so 20.8 / 0.6 / 3.6 x 1000 = about 9,700mAh or more.

The voltage and efficiency are set to the unfavorable end so the result doesn’t err toward “enough”.

Assuming 60-70% efficiency and a 0% to 100% charge, if you use the bank in flight and still want a charge after landing, add the two. A phone alone then needs about 41.6Wh, and 20,000mAh just barely covers it.

In the calculator, pick your devices, whether you fly a Japanese or US airline, and whether you use the bank in flight. It shows the size you need and whether you can carry it on.

Picks for each situation

Candidates have 100 or more ratings, 4.0 or more stars, an Amazon or maker seller, and no recall. Of the products checked here, these are the cheapest that meet the conditions (as of October 2026).

Phone only

10,000mAh just barely covers one phone charge on a layover or after landing, with about 0.8Wh to spare. The iPhone 18 Pro Max figure is from EU labels as reported by the press (Apple does not publish it), and the US models are unchecked.

An iPad Air 11-inch or Switch 2 besides your phone, after landing

20,000mAh with two or more output ports, so it charges two devices at once. In flight, a phone plus an iPad Air 11-inch needs 25,000mAh (just barely); use the pick below.

Phone plus a MacBook Air 13-inch, or an iPad Air 11-inch in flight, borderline

To charge a MacBook Air 13-inch too, pick a 25,000mAh bank that can put out USB PD 65W or more from a single USB-C port. Check the maximum of one port, not the total. Anker lists the A1383 at 87W total with 65W per port, and the A1695 at 165W total with 100W per port.

Sold by AnkerDirect, the maker's official store.

FAQ

Can I bring a 20,000mAh power bank on a plane?

Converting at a 3.6-3.85V cell voltage, 20,000mAh is about 72-77Wh, inside both Japan’s 160Wh and the FAA’s 100Wh limits. Under FAA rules as of October 2026, power banks of 100Wh or less can be carried on without airline approval.

Those of 101 to 160Wh need the airline’s approval, and none can go in checked baggage. 20,000mAh is about 77Wh even at 3.85V, and 25,000mAh about 96Wh, both inside the 100Wh limit.

How many power banks can I bring on a plane?

Under Southwest’s rules as of October 2026, Southwest allows only 1 power bank per person. Airlines may set stricter limits than the FAA, so check your airline’s rules.

Under Japan’s rules since April 24, 2026, on Japanese airlines you may carry up to 2 power banks of 160Wh or less, none in checked baggage.

Can I use a power bank on the plane?

Under Japan’s rules since April 24, 2026, on Japanese airlines you may not charge a bank or charge a device from one on board. You may carry up to 2 banks of 160Wh or less, none in checked baggage.

Application to foreign airlines has not been checked. For other airlines, check the rules before you count on charging in flight.

What size power bank do I need for a long-haul flight?

Assuming your airline allows use in flight, 60% efficiency and one full charge per device (half for a laptop), a phone alone just barely gets by on 10,000mAh. Adding a Switch 2 raises it to 20,000mAh and adding an iPad Air 11-inch to 25,000mAh, both just barely.

A phone plus half a MacBook Air 13-inch charge needs 25,000mAh. The size depends on your charges, not flight hours.

The table counts one full charge each, for hours of video or play, and half for a laptop used for a few hours.

Do I still need a power bank if my seat has power?

Seat power may reduce how much backup capacity you need, but only if your seat has it. Per American Airlines as of October 2026, American says most of its planes have AC or USB power at each seat.

If yours does, try charging from the seat in flight and keep the bank for after landing. Not every plane has it, and the seat’s output and its fit with your devices have not been checked, so do not count on it.

Do I need a power bank for a layover?

If you want to charge your phone on a layover, a bank helps when the airport has no outlet. Assuming 60% efficiency and, on a layover or after landing, one full phone charge (half for other devices), a phone alone just barely gets by on 10,000mAh.

Add an iPad Air 11-inch or Switch 2 and you need 20,000mAh, and a MacBook Air 13-inch needs 25,000mAh.