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Energy
Watt-Hours Calculator
Convert battery mAh and voltage to watt-hours.
Energy
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Watt-hours.
| Airline carry-on | — |
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| Capacity | — |
| Voltage | — |
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How the Watt-Hours Calculator Works
Watt-hours measure how much energy a battery holds, which is more meaningful than milliamp-hours alone because it accounts for voltage. Multiply the capacity in mAh by the voltage and divide by 1,000. A 20,000 mAh power bank at 3.7 volts is 74 watt-hours.
Airlines use watt-hours for lithium battery limits: up to 100 Wh is fine in carry-on, 100–160 Wh needs airline approval, and above 160 Wh is generally not allowed. Power banks list mAh at the cell voltage (usually 3.6–3.7 V), so this is the number to check before you fly.
watt-hours = mAh × voltage ÷ 1000
Frequently Asked Questions
How do you convert mAh to watt-hours?
Multiply the mAh by the battery voltage and divide by 1,000. A 10,000 mAh battery at 3.7 V is 37 Wh.
What is the airline limit for power banks?
Up to 100 Wh is allowed in carry-on without approval, 100–160 Wh needs airline approval, and over 160 Wh is generally prohibited.
What voltage should I use?
The battery’s nominal cell voltage, usually 3.6–3.7 V for lithium-ion power banks — not the 5 V USB output.
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