Power bank capacity is printed in mAh, but you never get the full figure in practice. This tool estimates how many real-world charges you’ll actually get for your device.
Power Bank Calculator
Estimate how many full charges a power bank will give your device. Real-world results are lower than the raw mAh figures because of conversion losses.
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How this calculator works
We multiply the power bank’s capacity by a realistic efficiency factor (voltage conversion and heat lose energy), then divide by your device’s battery capacity. The default 80% efficiency reflects typical real-world performance; premium banks may do a little better, budget ones a little worse.
Example
A 20,000 mAh power bank at 80% efficiency charging a 3,200 mAh phone gives about 5 full charges — not the 6+ the raw numbers suggest.
Limitations
Actual results vary with cable quality, fast-charging losses, how warm the battery gets, device usage while charging, and battery age. Treat the number as a close estimate, not a guarantee.
Frequently asked questions
Why don’t I get the full mAh?
Power banks store energy at 3.7V but charge devices at 5V or higher. Converting voltage loses energy as heat, which is why real output is 60–85% of the label.
What efficiency should I use?
70–85% covers most real-world cases. Use 80% as a sensible default and drop toward 70% for very cheap banks or fast charging.