Convert battery milliamp-hours to watt-hours at any cell voltage (3.7 V lithium, 12 V lead-acid, 5 V power bank). Includes airline 100 Wh rules.
| Input | Result |
|---|---|
| 20000 mAh at 3.7 V | 74.00 Wh |
| 20000 mAh at 5 V | 100.00 Wh |
| 3000 mAh at 3.7 V | 11.10 Wh |
Multiply mAh by the cell voltage and divide by 1000: Wh = mAh × V ÷ 1000. A 20,000 mAh power bank at 3.7 V stores 74 Wh; the same 20,000 mAh at 5 V equals exactly 100 Wh.
IATA rules: batteries under 100 Wh go in carry-on freely, 100–160 Wh need airline approval, over 160 Wh are forbidden. Check the Wh value printed on the battery — or compute it here.
Use the cell's nominal voltage: 3.7 V for lithium-ion cells, 3.6–3.7 V for LiPo, 12 V for lead-acid, 1.5 V for alkaline. Power banks are often rated in mAh at cell voltage (3.7 V) while airlines list limits in Wh.