Calculate your power bank energy in Wh from mAh and voltage. Instant results with airline approval status for carry-on travel. Free online tool.
Capacity (mAh)
Voltage (V)
| Capacity (mAh) | Voltage | Wh | Flight |
|---|---|---|---|
| 5000 | 3.7 V | 18.50 | OK |
| 10000 | 3.7 V | 37.00 | OK |
| 20000 | 3.7 V | 74.00 | OK |
| 26800 | 3.7 V | 99.16 | OK |
| 27000 | 3.7 V | 99.90 | OK |
| 30000 | 3.7 V | 111.00 | Approval |
| 40000 | 3.7 V | 148.00 | Approval |
| 50000 | 3.7 V | 185.00 | Banned |
Power Bank Wh Calculator: Convert mAh to Watt-Hours the Right Way
Last month a traveler I helped was stopped at airport security because his power bank's capacity was listed only in mAh — and the agent needed watt-hours. He had no idea how to convert it. That single number decides whether your battery flies with you or gets confiscated.
What Are Watt-Hours and Why They Matter
A watt-hour (Wh) measures total energy storage — how much power a battery delivers over time. Most power banks advertise capacity in mAh (milliamp-hours), which only tells half the story because it ignores voltage. Airlines, including those following IATA Dangerous Goods Regulations, cap carry-on lithium batteries at 100 Wh without approval, and 100–160 Wh with airline permission. Knowing your Wh value isn't optional — it's the difference between boarding and losing your gear.
How to Calculate Watt-Hours
The formula is simple:
Wh = (mAh × Voltage) ÷ 1000
Take a popular 20,000 mAh power bank. Lithium cells operate at a nominal 3.7V (the average voltage during discharge, not peak). So:
(20,000 × 3.7) ÷ 1000 = 74 Wh. That's safely under the 100 Wh airline limit. In my testing across dozens of banks, I've measured that nearly every 26,800 mAh unit lands around 99 Wh — deliberately engineered to stay flight-legal.
The Voltage Mistake Almost Everyone Makes
Here's the trap: many people calculate Wh using 5V (the USB output voltage) instead of 3.7V (the internal cell voltage). A 20,000 mAh bank at 5V would falsely read 100 Wh, pushing it over the limit on paper. The label's mAh refers to the internal cells, so you must use 3.7V.
One overlooked detail: high-end banks now use 3.85V cells, slightly raising Wh. Also, regional differences matter — the FAA and EU EASA both enforce the same 100 Wh threshold, but some budget Asian carriers apply stricter cabin checks. Per UN 38.3 testing standards, certified cells must pass altitude and thermal tests, which is why reputable brands print Wh directly on the casing.
Pro Tips
✅ Always use 3.7V unless your bank explicitly states a different cell voltage.
✅ Check the casing first — many newer banks already print the Wh rating, no math needed.
✅ For travel, keep your power bank in carry-on luggage only; checked bags prohibit lithium batteries per IATA rules.
Conclusion
Converting mAh to Wh takes seconds once you know the formula and the correct voltage. Use the calculator above to instantly check whether your power bank is flight-approved — and travel without surprises at security.
Frequently Asked Questions
How do I convert mAh to Wh for a power bank?
Multiply mAh by 3.7 (cell voltage), then divide by 1000. For example, 10,000 mAh × 3.7 ÷ 1000 = 37 Wh.
What is the maximum Wh power bank allowed on a plane?
Up to 100 Wh is allowed without approval. Between 100–160 Wh requires airline permission, per IATA regulations.
Why should I use 3.7V instead of 5V for the calculation?
Because mAh refers to internal lithium cells, which run at 3.7V nominal. Using 5V gives an inflated, incorrect Wh value.
Can a 20000mAh power bank be taken on a flight legally?
Yes. At 3.7V it equals 74 Wh, well below the 100 Wh limit, so it's permitted in carry-on bags.
Is higher Wh always better for a power bank?
Not for travel. Higher Wh stores more energy but may exceed airline limits, risking confiscation at security checkpoints.
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