Power bank capacity explained: mAh, Wh and real charges

Power banks list capacity in milliamp-hours (mAh), but you will never get the full number into your phone.

Why the real number is lower

Energy is lost converting voltage and as heat. A rough rule is that a power bank delivers about two thirds of its listed capacity.

Watt-hours and flights

Airlines limit batteries by watt-hours (Wh). Many allow up to 100 Wh in carry-on bags without approval. Check your airline's rules.

Output wattage

If you want to charge a laptop, check the USB-C output in watts and the laptop's needs.

Checklist

• Capacity in mAh and Wh
• Output wattage per port
• Input charging speed
• Weight