Free tool
mAh to Wh Calculator: Formula, Chart and Flight Check
To convert mAh to Wh, multiply the mAh by the battery voltage and divide by 1,000. A portable charger runs at 3.7V, so a 20,000mAh power bank is 20,000 × 3.7 ÷ 1,000 = 74Wh. Type your number below for the watt-hours and an instant airline verdict.
mAh to Wh converter
Convert mAh to Wh in one step
Enter your power bank’s printed capacity and we turn it into watt-hours, the figure airlines actually use, then tell you whether it flies. The rule is the same across the US, UK and EU: under 100 watt-hours needs no approval, 100 to 160Wh needs airline permission, and over 160Wh is banned from passenger aircraft.
The big number on the box. Tap a common size:
Leave at 3.7V unless your bank states otherwise.
Enter a capacity
We will work out the watt-hours and tell you if it flies
If your bank prints a Wh figure on the casing, that printed number is what security goes by.
100Wh is about 27,000mAh. 160Wh is about 43,000mAh. Most consumer banks are well under the line.
The formula
How to convert mAh to Wh
The mAh to Wh formula is Wh = mAh × V ÷ 1,000. Milliamp-hours measure charge; multiplying by the voltage turns charge into energy, and dividing by 1,000 turns milliwatt-hours into watt-hours.
For a portable charger or phone battery, V is 3.7, the nominal voltage of a lithium-ion cell. So the quick version is: divide the mAh by 1,000, then multiply by 3.7.
Worked examples. A 10,000mAh portable charger is 10,000 × 3.7 ÷ 1,000 = 37Wh. A 20,000mAh power bank is 20,000 × 3.7 ÷ 1,000 = 74Wh, well under the 100Wh airline limit. A 3,000mAh camera battery rated at 7.2V is 3,000 × 7.2 ÷ 1,000 = 21.6Wh.
Why 3.7 volts? It is the nominal voltage of the lithium-ion cells inside every power bank, and the figure regulators and airlines assume when they set the 100Wh limit.
Do not use 5V. 5V is the USB output, not the cell voltage. Put 5V into the formula and a 20,000mAh power bank looks like 100Wh, right on the airline line, when its real figure is 74Wh.
Going the other way? The Wh to mAh formula is mAh = Wh × 1,000 ÷ V. At 3.7V, the 100Wh airline limit is about 27,000mAh, 148Wh is 40,000mAh and the 160Wh ceiling is about 43,000mAh.
Printed Wh wins. Some makers rate their cells at 3.6V or 3.85V, so a 20,000mAh bank may print 72Wh or 77Wh rather than 74Wh. If a Wh figure is printed on the casing, security goes by that number, not your arithmetic.
Why your phone gets less than the printed mAh. The mAh rating is measured at the cell’s own 3.7V, but the bank has to step up to 5V or more to charge a device, and some energy is lost as heat along the way. As a rule of thumb, expect roughly two thirds of the printed capacity to reach your phone. Our iPhone charges calculator does that per-model math for you.
Reference chart
mAh to Wh chart for common sizes
Worked out at 3.7V, the nominal voltage airlines assume. A printed figure can differ by a watt-hour or two if the maker rates its cells at 3.6V or 3.85V.
| Printed capacity | Watt-hours | Flight status |
|---|---|---|
| 3,000mAh | 11.1Wh | Allowed |
| 5,000mAh | 18.5Wh | Allowed |
| 10,000mAh | 37Wh | Allowed |
| 15,000mAh | 55.5Wh | Allowed |
| 20,000mAh | 74Wh | Allowed |
| 25,000mAh | 92.5Wh | Allowed |
| 26,800mAh | 99.2Wh | Allowed, just under |
| 27,000mAh | 99.9Wh | Allowed, just under |
| 30,000mAh | 111Wh | Approval needed |
| 40,000mAh | 148Wh | Approval needed |
| 43,000mAh | 159.1Wh | Approval needed |
| 50,000mAh | 185Wh | Banned |
Formula and bands per the ICAO and IATA framework that the US FAA, UK CAA and EASA all implement: Wh = mAh × 3.7 ÷ 1,000. Airline policy on counts and in-flight use varies on top.
Whatever the size
Six flight rules that always apply
Carry-on only. Power banks are banned from checked bags on every airline, worldwide.
Two banks maximum under the global baseline since March 27, 2026. Wizz Air, Emirates and Southwest allow only one.
Keep it within reach, on you, in the seat pocket or under the seat. Not in the overhead bin.
Do not recharge the bank on board, and on many airlines do not use it to charge devices either.
The rating must be readable. A worn or missing label is grounds for confiscation.
Never fly with a swollen or damaged bank. Recycle it before the trip, not after.
Why it matters
Why airlines measure in watt-hours, not mAh
A mAh figure only describes a battery at one particular voltage, so the same printed number can mean different amounts of stored energy in different devices. Watt-hours measure the energy itself, which is what matters when a lithium battery is sitting in a cabin at 35,000 feet.
That is why the IATA battery guidance, the UK CAA and the US FAA all write their limits in Wh, while power bank boxes shout the bigger mAh number. Our calculator bridges that gap: type in the marketing number, get back the regulatory one. Formula per the ICAO lithium-battery framework implemented by the UK CAA, EASA and US FAA.
Portable power stations cannot fly at all. Products like the EcoFlow RIVER (256Wh), Jackery Explorer 1000 (1,002Wh) and anything larger are well above the 160Wh absolute ceiling. They are banned from both cabin and hold on every airline. Ship them by road freight or buy at your destination.
Quick answers
Frequently asked questions
How do I convert mAh to Wh?
Divide the mAh by 1,000, then multiply by 3.7, the nominal voltage of lithium-ion cells. A 25,000mAh bank is 25 times 3.7, which is 92.5Wh. If a Wh figure is already printed on the casing, that number wins.
How do I convert Wh to mAh?
Multiply the Wh by 1,000, then divide by the voltage. At the 3.7V a portable charger uses, 100Wh is about 27,000mAh, 148Wh is 40,000mAh and 160Wh is about 43,000mAh.
Why does my power bank print a different Wh than the calculator gives?
Makers rate their cells at slightly different nominal voltages, usually between 3.6V and 3.85V. So a 20,000mAh bank can print anything from 72Wh to 77Wh. At the airport, the printed figure is the one that counts.
What is the biggest power bank I can fly with?
Without approval, 100Wh, which is about 27,000mAh. That is why so many travel banks cluster at 20,000 to 27,000mAh: it is the largest size that clears security with no paperwork in the UK, EU and US.
Is a 20,000mAh power bank allowed on a plane?
Yes. At 3.7V it works out to 74Wh, comfortably under the 100Wh limit, with no approval needed on any airline in the UK, EU or US.
Can I take a 30,000mAh power bank on a plane?
Only with advance airline approval. 30,000mAh is about 111Wh, in the 100 to 160Wh band, and several carriers including Ryanair and Wizz Air refuse power banks above 100Wh entirely.
How many mAh is 100Wh?
About 27,000mAh at the 3.7V nominal voltage airlines assume, and the 160Wh approval ceiling works out to about 43,000mAh. That maths is the reason 26,800mAh became the classic travel size: it is the biggest round number that clears the no-approval limit.
Is a 40,000mAh power bank allowed on a plane?
Only with advance airline approval. 40,000mAh converts to about 148Wh, which sits in the 100 to 160Wh permission band, and several carriers including Ryanair and Wizz Air refuse power banks above 100Wh entirely. For regular flying, stay at 27,000mAh or below.
What voltage should I use in the calculator?
Leave it at 3.7V. That is the nominal voltage of the lithium-ion cells inside a power bank and the figure regulators use to set the flight limits. Only change it if your bank’s label states a different nominal voltage, and if the label already prints a Wh figure, that printed number is what security goes by.
Can I take a portable power station on a plane?
No. Portable power stations like the EcoFlow RIVER 3 Plus (286Wh), Jackery Explorer 1000 v2 (1,070Wh) and BLUETTI AC70 (768Wh) are all well above the 160Wh absolute ceiling. They are banned from passenger aircraft entirely, including cabin and hold. Ship by road freight or buy at your destination. See our power station reviews to find one for home or camping use.
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