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Use this formula: Wh = V × (mAh ÷ 1,000). A 20,000 mAh power bank rated at 3.7 V is 74 Wh, so it falls below the FAA’s 100 Wh baseline limit for spare batteries. A 30,000 mAh model at the same voltage is 111 Wh and enters the airline-approval range. Power banks must travel in carry-on baggage, never checked luggage.
Why watt-hours matter more than milliamp-hours
Airlines regulate a power bank by the energy stored in its battery, expressed in watt-hours (Wh). Milliamp-hours (mAh) describe charge capacity but are incomplete without voltage. Two batteries with the same mAh rating can store different amounts of energy if their nominal voltages differ.
The FAA and IATA use the same relationship: multiply rated capacity in ampere-hours by nominal voltage. In symbols, Wh = Ah × V. Because consumer labels commonly use milliamp-hours, convert first: Ah = mAh ÷ 1,000. Combining the two steps gives Wh = V × (mAh ÷ 1,000).
Wh is an energy measure. Output wattage (W), such as a USB-C port’s 20 W or 100 W charging rate, is a separate specification. A high-output port does not automatically mean a high-Wh battery, and a high-Wh battery does not necessarily charge devices quickly.
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How to calculate a power bank’s Wh rating
Step 1: Find the capacity and voltage
Look for a printed Wh value first. If the manufacturer provides a Wh rating, use that value for airline decisions. If the label only shows mAh, find the battery’s nominal or rated voltage on the label, manual, or manufacturer specification.
Use the battery voltage used to state its stored energy, not a USB output voltage selected by a charging circuit. A port may output 5 V, 9 V, 12 V or another negotiated level while the internal battery has a different nominal voltage. Substituting an output setting can produce the wrong Wh figure.
Step 2: Convert mAh to Ah
Divide the printed milliamp-hours by 1,000. For example, 20,000 mAh becomes 20 Ah; 26,800 mAh becomes 26.8 Ah.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchStep 3: Multiply amp-hours by volts
Multiply the converted Ah value by the nominal voltage. Keep the voltage and capacity from the same battery rating. The result is watt-hours.
- Read the label: for example, 20,000 mAh and 3.7 V.
- Convert capacity: 20,000 ÷ 1,000 = 20 Ah.
- Multiply: 20 Ah × 3.7 V = 74 Wh.
- Compare the result with your operating airline’s current battery limits.
Step 4: Use the manufacturer’s printed Wh when available
Manufacturers may round values or use a particular rated voltage. If a Wh number is printed, it is the clearest value for an airline agent to verify. Keep a photo of the label or the product specification available if the marking is difficult to read, but do not rely on a calculation that conflicts with a clearly printed Wh rating.
Worked calculations for common power banks
| Label capacity | Nominal voltage | Calculation | Energy | FAA baseline result |
|---|---|---|---|---|
| 10,000 mAh | 3.7 V | 3.7 × (10,000 ÷ 1,000) | 37 Wh | Within the 0–100 Wh range |
| 20,000 mAh | 3.7 V | 3.7 × 20 | 74 Wh | Within the 0–100 Wh range |
| 26,800 mAh | 3.7 V | 3.7 × 26.8 | 99.16 Wh | Within the 0–100 Wh range |
| 30,000 mAh | 3.7 V | 3.7 × 30 | 111 Wh | Air-carrier approval range |
These examples assume the listed 3.7 V is the battery’s nominal voltage. The same mAh number at another nominal voltage produces another Wh result. For instance, you cannot classify every 20,000 mAh product as 74 Wh without checking its voltage and any printed Wh rating.
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Which voltage should you use?
Use nominal battery voltage
Use the nominal voltage stated for the battery’s energy rating. For many USB power banks, the label or technical specification lists a cell-side nominal voltage around 3.7 V, but the exact value must come from that product’s marking or manufacturer documentation. The formula is only as reliable as the voltage and capacity values you enter.
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USB output voltage describes what the power bank supplies to a connected device after its internal electronics convert battery power. It can change with the charging protocol or the connected device. It is not necessarily the voltage used to calculate the battery’s stored energy.
When the label is unclear
- Check all sides of the power bank, because Wh, mAh and voltage may be printed in different locations.
- Check the manufacturer’s specification for nominal voltage and rated Wh.
- Do not infer voltage from the port’s advertised charging rate.
- If no reliable voltage or Wh value is available, contact the manufacturer or choose a clearly marked battery before flying.
FAA power-bank limits for passenger aircraft
The FAA classifies a power bank as a spare lithium-ion battery. Under the FAA baseline passenger rules, the battery’s Wh rating determines whether it can travel and whether airline approval is needed.
| Battery rating | FAA baseline treatment | Where it may be packed | Quantity or approval condition |
|---|---|---|---|
| 0–100 Wh | Allowed as a spare battery | Carry-on baggage only | Airline policies can impose additional limits |
| 101–160 Wh | Allowed only with air-carrier approval | Carry-on baggage only | Limited to two spare batteries per person under the FAA baseline |
| Over 160 Wh | Forbidden on passenger aircraft | Not permitted in carry-on or checked baggage | Do not bring it to the airport |
The 100 Wh boundary is inclusive: a battery rated exactly 100 Wh remains in the ordinary FAA range, while 101 Wh moves into the approval band. A calculated value such as 99.16 Wh is below the boundary, but the airline may still inspect the printed rating and apply its own policy.
What a 20,000 mAh battery means
A 20,000 mAh power bank rated at 3.7 V calculates to 74 Wh. That is below 100 Wh under the FAA baseline. You still must carry it in the cabin, protect its terminals, and comply with the operating carrier’s current rules.
What a 30,000 mAh battery means
At 3.7 V, 30,000 mAh calculates to 111 Wh. It is not an ordinary no-approval carry-on battery under the FAA baseline; it falls in the 101–160 Wh band, where the airline’s approval is required and no more than two spare batteries are allowed per person under that baseline. Approval is not guaranteed, so obtain it before departure rather than assuming the battery will be accepted at the gate.
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Where to pack a power bank
A power bank is a spare lithium-ion battery. Spare batteries must be in carry-on baggage and must not be placed in checked luggage. If your carry-on is taken at the gate and loaded into the aircraft hold, remove the power bank and keep it with you in the cabin.
Protect the terminals
Battery terminals must not contact metal objects such as keys, coins, tools or other batteries. A short circuit can cause overheating or fire. The FAA’s examples of protection include:
- Leaving the battery in its retail packaging.
- Covering exposed terminals with electrical tape.
- Placing the power bank in a battery case or sleeve.
- Keeping it in a protective pouch that prevents contact with metal items.
Prevent damage and isolate problems
Do not carry a power bank that is swollen, cracked, leaking, unusually hot, crushed or otherwise damaged. A battery subject to a safety recall and capable of sparking or overheating must not be carried unless it has been made safe according to the applicable safety instructions. Do not put a suspect battery in checked luggage as a workaround.
Keep it accessible
Place the protected battery where you can remove it for inspection. Keep its rating label legible. A clear label showing Wh, or mAh together with nominal voltage, makes it easier to resolve questions at security or the gate.
Carrier and international rules can be stricter
The FAA limits are a baseline for passenger aircraft, not a promise that every airline or country will accept the same quantity or packaging. The operating carrier can impose lower limits, require approval for batteries below a threshold, restrict use or recharging during the flight, or apply special rules to very large-capacity models.
Before leaving for the airport, check the current dangerous-goods or spare-battery page for every operating carrier on your itinerary, including codeshare segments. Confirm:
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- The maximum Wh per power bank.
- Whether approval is needed and how to obtain it.
- The number of spare batteries permitted per passenger.
- Whether the airline requires individual bags, terminal covers or other protection.
- Any restrictions on using or charging a power bank during the flight.
International authorities and airports can apply requirements that are stricter than the FAA baseline. A battery that is lawful under one jurisdiction’s general rule can still be refused by the carrier operating your flight. The carrier’s current policy is the rule that controls your trip.
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Wh versus watts: the specification that often causes confusion
| Specification | What it describes | Why it matters for travel |
|---|---|---|
| Watt-hours (Wh) | Total stored energy, calculated from nominal voltage and amp-hours | Primary battery-size measure used for airline limits |
| Milliamp-hours (mAh) | Charge capacity at a stated or implied voltage | Must be converted with voltage before comparing batteries |
| Voltage (V) | Electrical potential used with Ah in the Wh calculation | Must be the battery’s nominal voltage, not an arbitrary USB output |
| Output watts (W) | Maximum instantaneous charging power delivered by a port | Indicates charging speed and compatibility, not airline energy classification |
For example, a 74 Wh power bank might advertise a 100 W USB-C output. The 100 W figure says how quickly it may deliver power under supported conditions; it does not turn the battery into a 100 Wh or 100 W-h battery. Conversely, a battery can have a large Wh rating while offering modest output power.
How to choose a power bank for a flight
Start with the battery’s legally decisive measurement: Wh per individual power bank. Then evaluate practical features that affect whether it will be useful and easy to carry.
| Comparison point | What to check | Why it matters |
|---|---|---|
| Labeled Wh | Printed Wh value or a calculation supported by nominal voltage | Determines the airline category; a clear label reduces disputes |
| mAh and nominal voltage | Both values shown consistently on the product | Allows you to verify Wh when only mAh is prominent |
| Physical size and weight | Dimensions and mass that fit your personal item | A high-capacity model may be inconvenient even when permitted |
| Output ports | Port type, number of devices and supported protocols | Determines whether it can charge your phone, tablet or laptop |
| Charging speed | Maximum output watts and input charging rate | Affects how quickly devices charge and how quickly the bank refills |
| Markings and documentation | Legible model, capacity, voltage and safety information | Useful for inspection and for confirming the airline category |
| Carrier policy | Current Wh, quantity, approval and packing rules | Airlines and international authorities may be stricter than the FAA baseline |
Why a 100 Wh model is a practical target
A power bank at or below 100 Wh stays within the FAA’s ordinary range without the 101–160 Wh approval step. That does not waive carry-on and short-circuit requirements, and it does not override a stricter carrier rule. When shopping, verify the product’s printed Wh rating rather than relying on a marketing mAh number alone.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common calculation and packing mistakes
Comparing mAh values without voltage
mAh alone cannot establish energy. Always obtain nominal voltage and apply the conversion, or use the printed Wh rating.
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Using 20,000 directly as Ah would produce an answer 1,000 times too large. The correct conversion is 20,000 mAh ÷ 1,000 = 20 Ah.
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Using the wrong voltage
A USB port’s 5 V, 9 V or 12 V output is not automatically the battery voltage. Use the nominal voltage specified for the stored-energy rating.
Rounding a borderline battery down
Do not round a value just below or above a regulatory boundary without checking the label. The 26,800 mAh at 3.7 V example is 99.16 Wh, while 30,000 mAh at 3.7 V is 111 Wh. Those are different airline categories.
Putting a spare battery in checked baggage
Checking a power bank does not make it compliant. Spare power banks belong in carry-on baggage, protected against short circuits.
Assuming FAA rules are the only rules
The operating carrier and international authorities may set stricter limits or procedures. Confirm the policy for the actual flight, not only a general aviation rule found elsewhere.
Preflight checklist
- Read the power bank’s printed Wh rating. If none is printed, record the labeled mAh and nominal voltage.
- Calculate
Wh = V × (mAh ÷ 1,000)and retain the arithmetic for your records. - Classify the battery: 0–100 Wh, 101–160 Wh requiring airline approval, or over 160 Wh and forbidden under the FAA baseline.
- Check every operating carrier’s current power-bank policy, including quantity and approval requirements.
- Confirm that the battery is not swollen, damaged, recalled or otherwise unsafe.
- Cover terminals or place the battery in retail packaging, a case, sleeve or protective pouch.
- Pack it in your carry-on, where the label and protection can be shown during inspection.
- If your carry-on is gate-checked, remove the power bank before it enters the hold.
Quick answers to the most common scenarios
Can I bring a 20,000 mAh power bank?
If it is rated at 3.7 V, it is 74 Wh and fits within the FAA’s 0–100 Wh baseline range. Carry it in the cabin with terminal protection and verify the airline’s current policy.
Is 26,800 mAh under the 100 Wh limit?
At 3.7 V, 26,800 mAh equals 99.16 Wh, which is below 100 Wh. Check the product’s printed Wh rating and the carrier’s policy before relying on the calculation.
Can I bring a 30,000 mAh power bank?
At 3.7 V, it calculates to 111 Wh. Under the FAA baseline, that requires air-carrier approval, is limited to two spare batteries per person, and must remain in carry-on baggage. A carrier can be stricter or refuse it.
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Can a power bank go in checked luggage?
No. Spare power banks must be carried in carry-on baggage, protected from short circuits and damage.
What if the power bank has no Wh marking?
Use the labeled or manufacturer-rated nominal voltage with the mAh-to-Ah conversion. If neither a reliable voltage nor a Wh rating is available, obtain documentation from the manufacturer or use a clearly labeled alternative.
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