How do I convert mAh to watt-hours?

Watt-hours = (mAh ÷ 1000) × voltage. Power banks are rated at their cell voltage, which is almost always 3.7 V, so a 20,000 mAh bank is 20 × 3.7 = 74 Wh, and a 10,000 mAh bank is 37 Wh. Use 3.7 V unless your battery clearly states otherwise — and if a Wh figure is printed on the label, just use that, since it’s the official rating airports check.

What size power bank is the limit — in mAh?

Because the cap is set in watt-hours, the mAh limit depends on voltage. At the standard 3.7 V, 100 Wh works out to about 27,000 mAh, which is exactly why so many travel power banks are sold at 26,800 or 27,000 mAh — they sit just under the no-approval ceiling. A 50,000 mAh bank is around 185 Wh, well over 160, so it can’t fly.

Why must power banks go in carry-on, not checked luggage?

Lithium-ion batteries can overheat and catch fire through a process called thermal runaway. In the cabin, crew can spot and tackle a smoking battery immediately; in the cargo hold a fire could grow undetected. That’s why every major regulator bans spare batteries and power banks from checked bags — if you accidentally check one, it can be confiscated or delay your bag.

Can I use my power bank during the flight?

Increasingly, not freely. Through 2025–2026 many airlines added rules against charging power banks from in-seat USB ports and against using them while they’re stowed in the overhead bin, and some routes (including a Japan-wide rule from April 2026) restrict in-flight use further. If you do use one, keep it visible and accessible, and always check your specific airline’s current policy before you travel.

🔋 Calculator

Power Bank on a Plane?

Convert your power bank’s mAh to watt-hours and see instantly whether it’s allowed on board — and under what conditions. Carry-on only, on every airline.

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Capacity (mAh)

Nominal voltage

✅

74.0 Wh

Allowed in your carry-on

Up to 100 Wh — generally allowed in hand luggage without airline approval. No quantity limit for personal use, though some airlines set their own cap.

Carry-on only. Power banks and spare batteries must go in your cabin bag — never in checked luggage, on every major airline. Protect the terminals (keep the packaging or tape them) and keep it accessible.

At 3.7 V, the 100 Wh “no-approval” ceiling is about 27,027 mAh — which is why travel power banks top out around 26,800–27,000 mAh. Newer batteries print the Wh on the label; use that if it’s shown.

Many airlines now restrict using or charging power banks in flight — and using them inside the overhead bin — with several new bans in 2026. Individual airlines and countries can also set stricter limits, and staff may refuse a battery whose Wh rating isn’t marked. Always check your airline before you fly.

General guidance based on IATA/FAA rules for lithium-ion batteries; not legal advice. Lithium-metal (non-rechargeable) batteries follow separate limits.

By SK KutubuddinReviewed May 2026

Quick Answer

Is my power bank allowed on a flight?

In carry-on only: up to 100 Wh (≈27,000 mAh at 3.7 V) is fine with no approval, 100–160 Wh needs airline approval and is limited to two spares, and over 160 Wh is banned from passenger aircraft. Never pack a power bank in checked baggage. Enter your capacity above for the exact watt-hours and verdict.

Carry-on, OK

≤ 100 Wh

Approval, max 2

100–160 Wh

Banned

> 160 Wh

27,000 mAh

100 Wh ≈

Methodology: The watt-hour thresholds — 100 Wh without approval, 100–160 Wh with approval (max two spares), over 160 Wh forbidden, and the carry-on-only rule — are the global standard from IATA’s Dangerous Goods Regulations, mirrored by the FAA, TSA, EASA and ICAO, re-checked against their 2026 guidance. The calculator uses Wh = (mAh ÷ 1000) × voltage, defaulting to the 3.7 V cell voltage that power-bank mAh ratings (and printed Wh figures) are based on. Because individual airlines and countries can be stricter and have added in-flight-use restrictions in 2026, the tool states plainly that you should confirm with your airline. General guidance, not legal advice. How we test & calculate.

The rule is set in watt-hours, not mAh

Power banks are sold in milliamp-hours (mAh), but airlines regulate them in watt-hours (Wh) — and that trips a lot of travellers up. To convert, multiply the capacity by the voltage: a power bank is rated at its cell voltage, which is almost always 3.7 V, so 10,000 mAh is 37 Wh and 20,000 mAh is 74 Wh. Newer batteries print the Wh straight on the label, and that’s the number an airport will look at, so use it if it’s there.

The three thresholds

Up to 100 Wh, your power bank is fine in carry-on with no approval needed — which covers almost every consumer power bank. Between 100 and 160 Wh you’re into large-camera and drone-battery territory: allowed in carry-on, but only with your airline’s approval, and no more than two spares. Above 160 Wh it’s not permitted on a passenger aircraft in any bag. At 3.7 V, 100 Wh is about 27,000 mAh, which is why travel power banks cluster at 26,800–27,000 mAh, and why a 50,000 mAh brick (≈185 Wh) can’t come along.

Always in the cabin, never in the hold

Whatever the size, spare batteries and power banks must travel in your carry-on, never in checked luggage. Lithium-ion cells can go into thermal runaway and catch fire, and a fire in the cabin can be dealt with by the crew while one in the cargo hold cannot. Keep terminals protected — original packaging or a strip of tape — and keep the battery somewhere you can reach it.

Check before you fly

Treat this as the baseline. Airlines and countries can be stricter, staff can refuse a battery with no visible Wh marking, and 2026 has brought new restrictions on actually using power banks in flight. Confirm your airline’s current policy, and while you’re packing, run your liquids past the carry-on liquids rule and your bag past the carry-on size checker.

Frequently Asked Questions

Yes, in your carry-on — never in checked baggage. A power bank up to 100 watt-hours (roughly 27,000 mAh at the usual 3.7 V) is allowed without airline approval. Between 100 and 160 Wh you need your airline’s approval and may carry at most two spares; above 160 Wh it isn’t allowed on a passenger flight at all. This is a global rule from IATA, the FAA, EASA and ICAO.