A 100Wh power bank stores 100 watt-hours of energy — the threshold U.S. rules use to decide whether you can fly with it in carry-on.
Wh and mAh measure the same battery two different ways, and only one of them decides whether airport security lets your power bank board. People memorize the printed mAh figure and assume that’s their answer. It isn’t. The number that matters at the checkpoint is watt-hours, and most power banks only print it in tiny type near the charging ports.
Here’s what the rating actually means, how to convert mAh to Wh in your head, and the exact air-travel rules based on the FAA and TSA guidance.
What Does Wh Actually Measure?
A watt-hour measures total energy: one watt of draw sustained for one hour. Watt-hours capture how much usable energy a battery holds, while milliamp-hours (mAh) only describe charge capacity at a specific voltage. Two packs rated 20,000mAh can carry different energy totals if their cells run at different voltages.
Because energy is voltage times charge, the same mAh figure translates to different Wh depending on the battery inside. This is why airline rules key off Wh — it’s the only apples-to-apples comparison across devices.
How Do You Convert mAh To Wh?
Multiply voltage by amp-hours: Wh = V × Ah. For milliamps, divide by 1,000 first, so the formula becomes Wh = V × mAh ÷ 1000. A 12V, 8Ah battery lands at 96Wh. Most consumer power banks use cells around 3.7V nominal, which puts a 100Wh pack at roughly 27,000mAh.
Run the numbers on a typical 20,000mAh bank: 3.7V × 20,000 ÷ 1000 = 74Wh. That sails under the limit. A 30,000mAh pack at the same voltage hits 111Wh — now you need airline approval before it flies.
The catch is nominal voltage. Manufacturers sometimes list output voltage (like 5V USB) rather than the cell’s internal voltage, which inflates the calculated Wh. When the label gives you both numbers, use the lower, cell-level voltage for travel math.
A Quick Conversion Reference
| Battery Rating | Energy In Wh | Air-Travel Status |
|---|---|---|
| 10,000mAh at 3.7V | 37Wh | Carry-on, no approval |
| 20,000mAh at 3.7V | 74Wh | Carry-on, no approval |
| 27,000mAh at 3.7V | ~100Wh | Carry-on, at the limit |
| 30,000mAh at 3.7V | 111Wh | Needs airline approval |
| 12V 8Ah battery | 96Wh | Carry-on, no approval |
| 43,000mAh at 3.7V | 159Wh | Needs airline approval |
| 45,000mAh at 3.7V | 167Wh | Not allowed on passenger aircraft |
What Are The Air-Travel Rules For Power Banks?
Spare lithium-ion batteries and power banks rated 100Wh or less can go in carry-on baggage without any special permission, according to the FAA’s guidance on airline passengers and batteries. Units between 101Wh and 160Wh require airline approval, and passengers may typically carry up to two of them. Anything above 160Wh is banned from passenger aircraft entirely. The TSA’s page on lithium batteries over 100 watt hours confirms the same structure.
The critical packing rule: spare batteries and power banks travel in carry-on only, never in checked luggage. Terminals should be protected against short circuit — tape over the contacts or keep the pack in its original pouch. The spare-battery category covers power banks, portable chargers, charging cases, phone and laptop batteries, and external batteries alike.
One labeling note: the Wh rating should be marked on the battery itself. If it isn’t, calculate it from the printed voltage and amp-hours before you pack. If the number is close to the limit and you can’t confirm it, expect questions at screening.
Three Mistakes That Get Packs Confiscated
- Assuming the printed mAh figure settles eligibility — only Wh does.
- Treating every 100Wh pack as identical when nominal voltage shifts the real number.
- Packing a spare power bank in checked baggage instead of carry-on.
Which 100Wh Power Bank Should You Buy?
For most travelers, a pack in the 74–100Wh range balances capacity against hassle: enough to recharge a phone several times, still simple to fly with. Anything above that trades convenience for paperwork.
If you want tested options instead of guessing from spec sheets, our roundup of the best 100Wh power banks for travel compares real capacities, port layouts, and charging speeds. For the underlying federal rules, the FAA’s airline passengers and batteries page is the source to check before any international trip.
Whatever you buy, verify the Wh rating printed on the case before your flight. That single number decides whether the pack flies or stays home.
FAQs
Is 100Wh the same as 100,000mAh?
No. At the 3.7V nominal voltage most power banks use, 100Wh equals roughly 27,000mAh, not 100,000mAh. The relationship depends entirely on voltage: Wh = V × mAh ÷ 1000. A pack claiming 100,000mAh at 3.7V would carry about 370Wh, far beyond what any airline allows in carry-on baggage.
Can I bring two 100Wh power banks on a plane?
Yes. Batteries at or under 100Wh fall under the unrestricted spare-battery allowance, so quantity limits come from the airline rather than the federal threshold. Keep every spare pack in carry-on baggage with the terminals taped or covered. Check your specific carrier’s policy before flying, since some airlines cap how many spares one passenger may bring.
What happens if my power bank has no Wh label?
Calculate it yourself: multiply the printed voltage by the amp-hours, or by mAh divided by 1000. Screeners may refuse a pack they cannot verify. If the math lands above 100Wh and you lack approval documentation, the safest move is leaving that pack at home and traveling with a clearly labeled, lower-rated unit instead.
References & Sources
- Federal Aviation Administration. “Airline Passengers and Batteries” Defines the 100Wh and 160Wh spare-battery limits and carry-on packing rules.
- Transportation Security Administration. “Lithium batteries with more than 100 watt hours” Explains the approval requirement for 101–160Wh batteries.
- Transportation Security Administration. “Lithium batteries with 100 watt hours or less, in a device” Covers the unrestricted carry-on allowance for batteries at or under 100Wh.