mAh to Wh chart for power banks
Most power banks use lithium-ion cells rated at 3.6 or 3.7 volts. The Wh printed on the label tells you which one your power bank uses. "Flying" assumes the higher 3.7 V figure, to be safe.
| Capacity | Wh at 3.6 V | Wh at 3.7 V | Flying |
|---|---|---|---|
| 5,000 mAh | 18 | 18.5 | Carry-on |
| 10,000 mAh | 36 | 37 | Carry-on |
| 15,000 mAh | 54 | 55.5 | Carry-on |
| 20,000 mAh | 72 | 74 | Carry-on |
| 24,000 mAh | 86.4 | 88.8 | Carry-on |
| 25,000 mAh | 90 | 92.5 | Carry-on |
| 26,800 mAh | 96.5 | 99.2 | Carry-on |
| 27,000 mAh | 97.2 | 99.9 | Carry-on |
| 30,000 mAh | 108 | 111 | Airline approval |
| 40,000 mAh | 144 | 148 | Airline approval |
| 50,000 mAh | 180 | 185 | Forbidden |
A 10,000 mAh power bank holds 36 to 37 Wh and a 20,000 mAh one 72 to 74 Wh. 26,800 and 27,000 mAh power banks come in just under 100 Wh at 3.7 V. A 30,000 mAh power bank is over the line at either voltage.
How to convert mAh to Wh
Divide the mAh by 1,000 to get amp-hours, then multiply by the voltage. This is the method the FAA gives, and IATA defines a battery's Wh rating the same way: rated capacity in amp-hours times nominal voltage.
- Wh = mAh × V ÷ 1,000. 20,000 mAh × 3.7 V ÷ 1,000 = 74 Wh.
- mAh = Wh × 1,000 ÷ V. 74 Wh × 1,000 ÷ 3.7 V = 20,000 mAh.
Use the battery's own voltage, not the 5 V of a USB port. Nitecore, for example, labels the NB20000 Gen 3 as 20,000 mAh at 3.6 V (72 Wh); Panasonic rates its NCR1865K 18650 cell at 3.6 V; Anker says most power banks use 3.7 V cells. American Airlines' own formula uses 3.7 V.
Wh to mAh: 100 Wh and 160 Wh in mAh
These are the capacities that line up with the two airline limits.
| Energy | mAh at 3.6 V | mAh at 3.7 V |
|---|---|---|
| 20 Wh | 5,556 | 5,405 |
| 37 Wh | 10,278 | 10,000 |
| 50 Wh | 13,889 | 13,514 |
| 72 Wh | 20,000 | 19,459 |
| 74 Wh | 20,556 | 20,000 |
| 99 Wh | 27,500 | 26,757 |
| 100 Wh | 27,778 | 27,027 |
| 160 Wh | 44,444 | 43,243 |
So 100 Wh is about 27,777 mAh at 3.6 V or27,027 mAh at 3.7 V. The biggest power bank you can carry on without asking the airline is around 27,000 mAh, and 160 Wh works out to about 43,243 to 44,444 mAh.
Why the 5 V "rated capacity" is lower
Some power banks print a second, smaller mAh figure, measured at the 5 V USB output. Nitecore lists the NB20000 Gen 3 as 20,000 mAh at 3.6 V and 10,100 mAh at 5 V. Two things shrink the number:
- Higher voltage, fewer mAh. The same 72 Wh is only 14,400 mAh at 5 V, because mAh does not account for voltage.
- Conversion loss. Raising the cell voltage to 5 V or more wastes some energy as heat. Nitecore's figures imply about 70% gets through. Anker puts a power bank's circuit at about 80 to 85% efficient.
For flying, always use the Wh rating, or the mAh at the cell voltage. Multiplying the headline mAh by 5 V overstates the energy: it would make a 20,000 mAh power bank look like 100 Wh.
Can you bring a power bank on a plane?
Yes, in your carry-on. The FAA sets the limits for flights in the US by the power bank's watt-hours:
| Power bank | Carry-on | Checked bag |
|---|---|---|
| Up to 100 Whabout 27,027 mAh at 3.7 V | Yes | No |
| 101–160 Wh | With airline approval, two at most | No |
| Over 160 Wh | No | No |
The FAA sets no quantity limit for power banks up to 100 Wh carried for personal use, but airlines can be stricter, and the big US airlines now are (see below). The battery terminals must be protected from short circuits: keep each power bank in its case, a pouch or the original packaging. Damaged or recalled batteries are not allowed at all.
Internationally, the rules tightened in 2026. ICAO, which writes the global rules for dangerous goods on planes, added an amendment on March 27, 2026 that limits passengers to two power banks and bans recharging a power bank on board. IATA's 2026 passenger guidance goes further: it lists power banks over 100 Wh as forbidden, even though larger spare batteries for cameras and laptops can still fly with approval.
TSA power bank rules
The TSA lists power banks as allowed in carry-on bags and not allowed in checked bags. TSA screening is about security; the size limits above come from the FAA and your airline. If your power bank has no Wh rating printed on it, check the manual or the maker's website before you fly: IATA's guidance says an airline may refuse a battery when staff can't confirm its Wh rating.
Can a power bank go in checked luggage?
No. Spare lithium batteries, including every power bank, have to stay in the cabin, where the crew can deal with one that overheats. If your carry-on gets checked at the gate or planeside, take the power banks out first and keep them with you. Laptops, phones and other devices with the battery built in can go in a checked bag if they are fully switched off, but the FAA recommends keeping them in the cabin too.
Airline power bank rules in 2026
Several US airlines now have their own power-bank rules on top of the FAA's. From each airline's website:
| Airline | Rules |
|---|---|
| Southwest |
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| American |
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| Delta |
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| JetBlue |
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On these airlines, a power bank over 100 Wh is not allowed even with approval. Rules change often and partner airlines can differ, so check the airline you're flying before you pack.
Are our power bank picks flight-safe?
Wh as published by the manufacturer where they list it; otherwise calculated from the capacity at 3.6 and 3.7 V.
| Power bank | Capacity | Energy | Flying |
|---|---|---|---|
| Belkin Boost Charge Plus 10KBest overall | 10,000 mAh | 36–37 Whcalculated | Carry-on |
| INIU Portable Charger 10000mAhBest budget | 10,000 mAh | 36–37 Whcalculated | Carry-on |
| Nitecore NB20000 Gen 3Best lightweight | 20,000 mAh | 72 Whstated, 3.6 V | Carry-on |
| Anker 325 Power Bank (PowerCore 20K)Our review | 20,000 mAh | 72–74 Whcalculated | Carry-on |
| Anker 737 Power Bank (PowerCore 24K)Best for laptops | 24,000 mAh | 86.4–88.8 Whcalculated | Carry-on |
All of them are under 100 Wh. The Anker 737 is the closest at up to 88.8 Wh, and it is the only one of these built to charge laptops. Since Southwest now allows one power bank, pick the one you need most if you fly with them. See all our picks in the best portable chargers and power banks.
How many charges will a power bank give?
Less than the mAh suggests. Energy is lost in the power bank's circuit and again inside the device while it charges. This calculator uses Anker's worked example: 82% through the power bank and 85% into the device's battery, so about 70% of the rated Wh ends up stored. Estimated full charges, with power banks at 3.7 V:
| Power bank | 5,000 mAh phone | iPad 11-inch (A16) | 13-inch MacBook Air (M5) | 14-inch MacBook Pro (M5) |
|---|---|---|---|---|
| 10,000 mAh37 Wh | 1.4 | 0.9 | 0.5 | 0.4 |
| 20,000 mAh74 Wh | 2.8 | 1.8 | 1.0 | 0.7 |
| 27,000 mAh99.9 Wh | 3.8 | 2.4 | 1.3 | 1.0 |
Device batteries are Apple's published ratings. The phone column assumes a 5,000 mAh phone battery at the same 3.7 V; check your phone's spec sheet for its capacity. Charging while you use the device, a cold battery or a slow cable all lower the count.
Power bank battery life: watt-hours to hours
To estimate how long a power bank can run something, divide the energy that reaches the USB port by the device's power draw in watts. A 20,000 mAh power bank at 3.7 V delivers about 60.7 Wh after the power bank's own losses, so a 10 W device would run for about 6 hours. Enter a wattage in the calculator to work it out.
How this calculator works
- Conversion: Wh = mAh × V ÷ 1,000, with V the battery's nominal cell voltage. You can enter any voltage; 3.6 and 3.7 V are the common power-bank ratings.
- Can I fly with it: the FAA limits of 100 Wh (no approval needed) and 160 Wh (with approval), plus the 2026 airline rules listed above.
- 5 V output: the Wh times 82%, divided by 5 V. A 20,000 mAh, 3.7 V power bank works out to about 12,136 mAh at 5 V.
- Charges: the 5 V energy times another 85% for losses inside the device, divided by the device battery's Wh. Both efficiency figures are from Anker's example; it gives ranges of 80 to 85% for the power bank and 80 to 90% for the device, so real results vary by a few percent either way.
Sources
- FAA PackSafe: Lithium batteries (updated August 11, 2026). faa.gov/hazmat/packsafe/lithium-batteries
- FAA: Airline passengers and batteries FAQ (updated October 2, 2026). faa.gov/hazmat/packsafe/airline-passengers-and-batteries
- TSA: What can I bring? Power banks. tsa.gov/travel/security-screening/whatcanibring/items/power-banks
- IATA: Passengers travelling with lithium batteries, guidance document revised for the 2026 regulations (March 31, 2026). iata.org/contentassets/6fea26dd84d24b26a7a1fd5788561d6e/passengers_tra…
- IATA: Changes regarding power banks, guidance for operators on the ICAO addendum of March 27, 2026. iata.org/contentassets/90f8038b0eea42069554b2f4530f49ea/guidance-to-op…
- Southwest Airlines: Traveling with lithium batteries and portable chargers. support.southwest.com/helpcenter/article/Traveling-with-lithium-batter…
- American Airlines: Restricted items in bags (batteries). aa.com/web/i18n/travel-info/baggage/restricted-items.html
- Delta Air Lines: Battery or fuel-powered items. delta.com/us/en/baggage/prohibited-or-restricted-items/battery-or-fuel…
- JetBlue: Batteries. jetblue.com/help/batteries
- Anker: Why is the rated capacity of power banks lower than expected? service.anker.com/article-description/Why-is-the-Rated-Capacity-of-Pow…
- Nitecore NB20000 Gen 3 specifications. flashlight.nitecore.com/product/nb20000gen3
- Panasonic Energy NCR1865K lithium-ion cell specifications (3.60 V nominal). energy.panasonic.com/na/business/products/lithium-ion/cylindrical-high…
- Apple: iPad 11-inch (A16) tech specs (28.93 Wh battery). apple.com/ipad-11/specs/
- Apple: 13-inch MacBook Air (M5) tech specs (53.8 Wh battery). apple.com/macbook-air/specs/
- Apple: 14-inch MacBook Pro (M5) tech specs (72.4 Wh battery). apple.com/macbook-pro/specs/
Rules and specifications checked October 7, 2026.