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Power Bank Charge-Count & Flight Checker

Quick answer

This calculator converts a power bank's mAh to honest watt-hours, see how many times it actually charges your phone (85% efficiency), and whether it passes the IATA 100 Wh

Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.

How does the Power Bank Charge-Count & Flight Checker work?

Wh = mAh × V ÷ 1000 | Charges = PB Wh × 0.85 ÷ device Wh | ≤100 Wh carry-on, 100–160 Wh approval, >160 Wh forbidden

mAh numbers are not comparable across voltages, and airlines set their limit in watt-hours, not milliamp-hours. This tool converts both the power bank and your device battery to watt-hours first, applies an 85% round-trip efficiency (covering the boost conversion from the 3.7 V cell to USB 5 V plus cable losses; independent measurements land between 75% and 90%), and divides to get the honest number of full charges. It then checks the watt-hours against the IATA lithium-battery limits for passengers: up to 100 Wh flies in carry-on without approval, 100–160 Wh needs the airline's prior approval (max two spares), and above 160 Wh is forbidden in passenger baggage.

  1. 1

    Step 1

    Enter the power bank's rated mAh (and its cell voltage, 3.7 V by default) — or its printed Wh if the listing shows it.

  2. 2

    Step 2

    Enter your device battery: its mAh (phones are typically 4000–5000 mAh at ~3.85 V) or its printed Wh.

  3. 3

    Step 3

    Read the watt-hours, the estimated charge count at 85% efficiency, and the aviation verdict under the IATA 100/160 Wh rules.

FAQs

Why doesn't a 20000 mAh power bank charge my 5000 mAh phone four times?

Because mAh is measured at the cell's voltage (3.7 V), while the phone charges over USB at 5 V. Converting to energy: 20000 mAh × 3.7 V = 74 Wh, and a 5000 mAh phone at 3.85 V holds ~19.25 Wh. After ~15% conversion and cable losses, 74 × 0.85 ÷ 19.25 ≈ 3.3 charges — not 4.

What is the airline limit for power banks?

Airlines work in watt-hours (Wh), following IATA lithium-battery guidance: up to 100 Wh in carry-on without approval; 100–160 Wh only with the airline's approval and a maximum of two spares; above 160 Wh forbidden in passenger baggage. At the usual 3.7 V, 100 Wh is about 27,000 mAh, which is why 20000 mAh banks fly freely.

Can I put a power bank in checked luggage?

No. Spare lithium batteries, including power banks, must always travel in carry-on baggage with terminals protected against short circuits, regardless of their size. Many airlines also prohibit charging devices from a power bank during the flight.

Are the charge-count numbers exact?

No — they are labeled estimates. The tool applies a fixed 85% round-trip efficiency; real power banks measure between roughly 75% and 90% depending on quality, charging speed and cable. The guaranteed full charges (rounded down) and the exact math are always shown so you can judge the estimate yourself.

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