Use Wh = V × (mAh ÷ 1,000). Convert the capacity from milliamp-hours to amp-hours, then multiply by the battery’s nominal voltage. A 20,000 mAh bank rated at 3.7 V is 74 Wh, so it falls within the FAA’s 0–100 Wh carry-on allowance. Power banks are spare lithium-ion batteries: keep them in carry-on baggage, protect their terminals, and check the operating airline’s rules before departure.
What watt-hours mean for a power bank
Watt-hours (Wh) measure stored battery energy. Airlines use Wh because it combines a battery’s electrical charge capacity with its voltage, giving one value that can be compared across batteries with different voltage ratings.
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Why mAh alone is incomplete
Milliamp-hours (mAh) describe charge capacity, not total energy. The same mAh number can represent different amounts of energy at different voltages. For that reason, a label showing only “20,000 mAh” does not fully identify the battery’s airline-relevant capacity until its rated voltage is known.
The FAA and IATA method
The FAA explains the calculation this way: “To determine Wh, multiply the volts (V) by the amp hours (Ah). For milliamp hours (mAh), divide mAh by 1000 (to get to Ah) and then multiply by the V.” IATA describes the same relationship as rated capacity in ampere-hours multiplied by nominal voltage: Wh = Ah × V.
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Wh is the legally decisive capacity measure for a power bank. Output wattage, shown in watts (W), describes how quickly the bank can deliver power to a device and is a separate specification.
Convert mAh to Wh in three steps
- Find the battery’s rated voltage. Use the nominal or manufacturer-rated voltage printed on the bank or in its technical specifications.
- Convert mAh to Ah. Divide the mAh figure by 1,000. For example, 20,000 mAh becomes 20 Ah.
- Multiply amp-hours by volts. Multiply the converted Ah value by the rated voltage to obtain Wh.
The complete equation is Wh = V × (mAh ÷ 1,000). Keep the voltage and capacity from the same battery rating; do not substitute a USB output voltage for the nominal battery voltage.
Worked calculations
| Labelled capacity | Rated voltage | Converted capacity | Calculation | Energy |
|---|---|---|---|---|
| 10,000 mAh | 3.7 V | 10 Ah | 3.7 × 10 | 37 Wh |
| 20,000 mAh | 3.7 V | 20 Ah | 3.7 × 20 | 74 Wh |
| 26,800 mAh | 3.7 V | 26.8 Ah | 3.7 × 26.8 | 99.16 Wh |
| 30,000 mAh | 3.7 V | 30 Ah | 3.7 × 30 | 111 Wh |
Under the FAA baseline, the first three examples are at or below 100 Wh. The 30,000 mAh example is 111 Wh, placing it in the 101–160 Wh airline-approval band. Use the manufacturer’s printed Wh rating whenever one is provided rather than replacing it with a rough calculation.
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Which voltage should you use?
Use nominal battery voltage
For airline calculations, use the battery’s nominal voltage or the voltage the manufacturer uses to state its energy capacity. This is normally identified in the specifications alongside the cell capacity or Wh rating.
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Do not use USB output voltage
A power bank may advertise 5 V, 9 V, or another USB output mode for charging a phone or laptop. Those are output settings, not necessarily the voltage used to rate the stored battery energy. Substituting an output value can produce the wrong Wh result and an incorrect airline classification.
When the label gives both mAh and Wh
Use the printed Wh figure for travel documentation and screening. The manufacturer has already applied its rated voltage and may have rounded the result for the product label. Keep a photo of the label or the manufacturer’s specification page if the printed markings are difficult to read.
When only mAh is shown
Look for the nominal voltage elsewhere on the bank, its packaging, or the manufacturer’s technical documentation. If no rated voltage can be established, you cannot calculate a reliable Wh value from mAh alone. Do not guess from a USB port’s voltage.
FAA passenger-aircraft thresholds
The FAA treats power banks as spare lithium-ion batteries. Its baseline limits are based on the Wh rating of each battery.
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| Power-bank rating | FAA baseline treatment | Approval and quantity |
|---|---|---|
| 0–100 Wh | Allowed as a spare battery in carry-on baggage | No FAA approval required under the baseline rule |
| 101–160 Wh | Carry-on only | Air-carrier approval required; no more than two spare batteries per person under the FAA baseline |
| Over 160 Wh | Not permitted on passenger aircraft | Forbidden regardless of carry-on or checked-bag placement |
Why 100 Wh is the practical target
A power bank rated at 100 Wh or less normally avoids the FAA approval requirement. That is why a clearly labelled model near, but not above, 100 Wh is often the simplest choice for air travel. A calculated 99.16 Wh result, such as 26,800 mAh at 3.7 V, is below the 100 Wh threshold; a 111 Wh result is not.
Approval is not a guarantee of carriage
The 101–160 Wh allowance is conditional. The operating carrier must approve the battery, and the FAA baseline limits a passenger to two spare batteries in that range. An airline can impose a lower limit, require a particular approval process, or prohibit a category that the FAA baseline would otherwise allow.
How to pack a power bank for a flight
Because a power bank is a spare battery, place it in carry-on baggage, never in checked baggage. Keep it accessible if staff need to inspect the label or remove it from a bag.
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Battery terminals must not touch metal objects or another conductor. The FAA’s lithium-battery guidance gives several acceptable protection methods:
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- Leave the battery in its original retail packaging.
- Cover exposed terminals with nonconductive tape.
- Put the bank in a battery case or sleeve.
- Place it in a protective pouch that prevents contact with keys, coins, cables, or other metal items.
The goal is to prevent a short circuit and to keep the battery from being crushed or punctured by other contents.
Do not carry a damaged or recalled bank
A battery that is swollen, cracked, leaking, unusually hot, or otherwise damaged can spark or overheat. Damaged or recalled batteries that could create those hazards must not be carried unless they have been made safe. Replace a questionable bank before the trip rather than trying to conceal or improvise protection for it.
If your carry-on is checked at the gate
If an airline takes your carry-on at the gate for loading in the hold, remove the power bank and keep it with you in the passenger cabin. A spare battery should not be transferred to checked baggage.
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FAA limits are a baseline for flights under its jurisdiction, not a promise that every carrier will accept every battery. International authorities and airlines may apply stricter rules, including lower Wh limits, tighter quantity limits, or approval requirements for batteries below 160 Wh.
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- Identify every power bank you intend to bring and record the printed Wh rating.
- Check the rules of the airline operating each flight, including connecting carriers. The operating carrier’s policy controls the practical acceptance decision.
- Look specifically for spare-battery quantity limits, approval procedures, and any restrictions on where the batteries may be stored in the cabin.
- Confirm the policy shortly before departure because airline and government requirements can change.
- Keep the bank’s label readable so its capacity can be verified during screening.
What to do when policies differ
Follow the strictest applicable requirement. A bank that meets the FAA’s 100 Wh baseline can still be refused if the airline sets a lower limit or a different quantity rule. For a 101–160 Wh battery, obtain the carrier’s approval before arriving at the airport; do not assume that approval will be granted at the security checkpoint.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to compare power banks for travel
Capacity is only one part of a useful travel choice. Compare the following attributes, while treating the Wh rating and the airline’s policy as the compliance checks that come first.
| Specification | What to check | Why it matters |
|---|---|---|
| Printed Wh rating | Exact Wh value on the product or manufacturer documentation | Determines the airline category |
| mAh and nominal voltage | Both figures, if Wh is not printed | Lets you verify the Wh calculation |
| Physical size and weight | Whether the bank fits your personal item and remains comfortable to carry | A larger capacity can add bulk even when it is permitted |
| Output ports | Number, connector type, and simultaneous-use limits | Determines how many devices can be connected and which cables you need |
| Charging speed | Advertised output wattage and supported charging standards | Controls how quickly devices recharge; it does not change the bank’s Wh classification |
| Manufacturer labelling | Readable capacity, voltage, and safety markings | Clear markings make screening and verification easier |
| Carrier policy | Current carry-on, approval, and quantity requirements | Can be stricter than the FAA baseline |
A checklist for a 100 Wh-class purchase
- Confirm that the product itself states a Wh rating at or below 100 Wh, not merely a marketing mAh number.
- If only mAh is shown, verify the nominal voltage and calculate the result before buying.
- Check that the rating is printed on the bank or supported by manufacturer documentation you can access while travelling.
- Choose a size and weight you can keep in your carry-on for the entire journey.
- Match the ports and charging speed to your devices, treating output W as a convenience specification rather than an airline limit.
- Review the operating airline’s current rules before ordering and again before departure.
Common calculation and packing errors
| Error | Correct approach |
|---|---|
| Multiplying mAh directly by volts | Divide mAh by 1,000 first so the capacity is in Ah. |
| Using a USB output value as the battery voltage | Use the nominal voltage associated with the stored battery capacity. |
| Ignoring a printed Wh value | Use the manufacturer’s stated Wh rating when available. |
| Relying on a rounded online listing | Read the physical label or the manufacturer’s specification and carry the exact value forward. |
| Putting a power bank in checked luggage | Keep every spare power bank in carry-on baggage. |
| Leaving terminals exposed | Use retail packaging, tape, a case, sleeve, or protective pouch. |
| Assuming FAA limits are universal | Check each operating airline and any applicable international authority for stricter rules. |
| Travelling with a swollen, cracked, or recalled battery | Do not carry it unless it has been made safe; replace it instead. |
Quick examples for common questions
Can a 20,000 mAh power bank go on a plane?
At the 3.7 V rating used in the worked example, 20,000 mAh equals 74 Wh. That is within the FAA’s 0–100 Wh baseline, so it may travel in carry-on baggage when properly protected. The airline’s own rules still apply.
Is a 26,800 mAh bank under the limit?
At 3.7 V, the calculation is 3.7 × 26.8 = 99.16 Wh. It is below 100 Wh under the FAA baseline. Confirm the actual product’s printed Wh rating because a different voltage or manufacturer rating changes the result.
Why can a 30,000 mAh bank require approval?
At 3.7 V, 30,000 mAh is 111 Wh, which is above the ordinary 100 Wh limit and falls into the 101–160 Wh approval band. The operating airline must approve it, and the FAA baseline allows no more than two such spare batteries per person.
Before you leave for the airport
Write down the Wh rating for each bank, verify that every one is permitted by the operating carrier, and pack them where they remain in the cabin. Check the terminals, remove any damaged unit, and keep the capacity label legible. The decisive calculation remains Wh = V × (mAh ÷ 1,000); the decisive travel location is carry-on baggage.
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