How Many Charges Does a 20,000mAh Power Bank Really Give You?
If you want the short answer, a 20,000mAh power bank does not give you a clean 4 full charges on a 5,000mAh phone battery. Real-world conversion losses usually drag that down.
The catch is manufacturers sell the headline capacity, but your device only sees the usable part after voltage conversion, heat loss and cable inefficiency.
Need your own estimate?
Use the Power Bank Capacity Calculator and plug in your bank and device size.
Use the Power Bank Capacity Calculator and plug in your bank and device size.
A rough rule of thumb
At around 75% efficiency, a 20,000mAh power bank gives you roughly 15,000mAh usable. If your phone battery is 5,000mAh, that works out to about 3 full charges, not 4.
Why the number falls short
- Voltage conversion losses
- Heat during charging
- Cable quality
- Fast-charge overhead
Bottom line
Expect less than the sticker number and you will buy smarter. Use the calculator before you choose a bank for travel or work.