Battery Charging Time Calculator
Estimate how long it will take to charge your battery based on its capacity, current charge, and charger power.
Estimated charging time
43 min
Charging from 20% to 100%. Real time varies with device, charger and battery condition.
Charge needed
80%
3,200 mAh of the pack.
Time in minutes
43 min
Energy required
12.3 Wh
Effective charging power
17 W
20 W charger at 85% efficiency.
Summary
80% in 43 min
- Runs entirely in your browser
- No data is stored
- Free forever
What is this calculator?
This calculator estimates charging time for a phone, tablet or power bank. Enter the battery capacity in mAh, where the charge sits now, where you want it to be, the wattage of your charger and a rough efficiency figure, and it returns the energy required and the time it should take. Handy for working out whether a quick top-up before you leave is realistic.
How does it work?
We convert mAh to watt-hours at a nominal 3.85 V, take the share of the pack you still need, then divide that energy by your charger wattage adjusted for efficiency. Real chargers slow down above 80 percent, so treat the answer as an optimistic estimate.
Frequently asked questions
Why is my real charging time longer?+
Devices slow charging above roughly 80 percent to protect the cell, and heat makes them throttle further. Real time is usually longer than the ideal figure.
What efficiency should I use?+
80 to 90 percent covers most chargers. Wireless charging is far less efficient, so try 60 to 70 percent there.
Where do I find my battery capacity?+
It is printed on the battery, listed in the device specifications, or easy to find by searching your exact model.
Does a bigger charger always charge faster?+
Only up to what the device accepts. A 100 W charger on a phone limited to 20 W still charges at 20 W.
Why 3.85 volts?+
It is the nominal voltage of a typical lithium-ion cell, which converts mAh into watt-hours so the charger wattage can be applied.
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