Lithium Battery Checker
A 20 000 mAh power bank is 74 Wh — comfortably under every limit. Calculate it with the 5 V from the USB port instead of the cell voltage and you get 100 Wh, exactly on the threshold, and you go asking an airline for permission you never needed. That one substitution is where most of these answers go wrong.
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Watt hours, and the voltage that decides them
Watt hours are milliamp hours divided by a thousand, times volts. The arithmetic is trivial; the voltage is not. A capacity in mAh is rated at the cell's nominal voltage — 3.6 or 3.7 V for most lithium-ion — not at whatever the device outputs. Using 5 V inflates the figure by about a third, which is precisely enough to cross the 100 Wh line.
If the battery has a Wh figure printed on it, use that and skip the calculation entirely. It is the manufacturer's own number and it is what an airline will read.
When no voltage is given, this page shows the reading at each common nominal voltage rather than picking one — a 10 000 mAh pack is 36 Wh at 3.6 V and 111 Wh at 11.1 V, which are two different answers to the question you asked.
The bands
- Up to 100 Wh — the ordinary case, no approval needed.
- 101–160 Wh — airline approval, and at most two spares per passenger.
- Above 160 Wh — not permitted in passenger baggage at all.
Lithium metal batteries are measured differently: by lithium content, with the same structure at 2 g and 8 g.
And the rule sellers most often miss: spare batteries and power banks travel in the cabin, never in checked baggage. If a cabin bag is checked at the gate, the spares have to come out first.
Where this tool stops
These are the published rules for what a passenger may carry. Shipping batteries as cargo is governed by the IATA Dangerous Goods Regulations and its packing instructions — a paid standard this project does not have. Reconstructing that decision tree from memory would produce confident, wrong answers about a safety matter, so this page says plainly that it stops here and points you at your carrier.
For the same reason: this is a calculator and a summary of published rules. It is not a compliance determination, and the airline's own current policy is the one that governs.
Every check this tool runs (10 rules)
LI-V01 That voltage looks like the USB output
A capacity in mAh is rated at the cell’s nominal voltage — 3.6 or 3.7 V for most lithium-ion — not at the 5 V a USB port delivers. Using 5 V inflates the watt-hour figure by about a third, which is exactly enough to push a 20 000 mAh pack from roughly 74 Wh to the 100 Wh threshold and make an ordinary battery look like one needing airline approval.
Fix: Use the cell voltage printed on the battery. If only the output voltage is marked, the Wh rating is usually printed too — use that instead of calculating.
Source: FAA PackSafe — Lithium Batteries
LI-T01 Under 100 Wh
Lithium-ion batteries rated at 100 watt hours or less are the ordinary case: no airline approval is needed, and there is no quantity limit for batteries in personal devices.
Source: FAA PackSafe — Lithium Batteries
LI-T02 101–160 Wh — airline approval, two spares maximum
Between 101 and 160 watt hours a battery may be carried only with the airline’s approval, and a passenger may carry at most two such spares. This band covers extended-life laptop batteries and larger professional audio-visual packs.
Fix: Contact the airline before travel. Approval is per airline, not universal.
Source: FAA PackSafe — Lithium Batteries
LI-T03 Over 160 Wh — not permitted in passenger baggage
Above 160 watt hours a lithium-ion battery cannot travel in passenger baggage at all, with or without approval. Batteries this size move as cargo under dangerous-goods rules.
Fix: Ship it as cargo through a carrier that handles dangerous goods — see the note below about what this tool does not cover.
Source: FAA PackSafe — Lithium Batteries
LI-M01 Lithium metal up to 2 grams
Lithium metal (non-rechargeable) batteries are measured by lithium content rather than watt hours. Up to 2 grams per battery is the ordinary case.
Source: FAA PackSafe — Lithium Batteries
LI-M02 Lithium metal 2–8 grams — airline approval
Between 2 and 8 grams of lithium content, the same approval and two-spare limit applies as for the 101–160 Wh band.
Source: FAA PackSafe — Lithium Batteries
LI-M03 Lithium metal over 8 grams
Above 8 grams of lithium content a battery is not permitted in passenger baggage.
Source: FAA PackSafe — Lithium Batteries
LI-S01 Spares are carry-on only
Spare batteries and power banks must travel in the cabin, never in checked baggage — and if a cabin bag is checked at the gate, the spares have to come out and stay with the passenger. Terminals must be protected against short circuit. This catches sellers out because it applies to the battery they ship as an accessory, not just the one inside the device.
Source: FAA PackSafe — Lithium Batteries
LI-B01 Cargo classification is not covered here
These are the published rules for what a passenger may carry. Shipping batteries as cargo is governed by the IATA Dangerous Goods Regulations and its packing instructions (PI 965–970), which are a paid standard this project does not carry. Rather than reconstructing that decision tree from memory and giving confidently wrong answers about a safety matter, this tool says plainly that it stops here.
Fix: For cargo shipments, ask your freight forwarder or carrier for the current packing instruction.
Source: FAA PackSafe — Lithium Batteries
LI-E01 Not enough to calculate
A watt-hour figure needs a capacity in mAh and a voltage, or a Wh rating directly.
Source: Derived from the definition of the watt hour.
Thresholds come from FAA PackSafe — Lithium Batteries. Cargo packing instructions are deliberately absent rather than approximated.