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Battery Life Calculator
Battery life in hours equals capacity in milliamp-hours divided by the load current in milliamps, adjusted for the fact that most batteries deliver slightly less than their nominal rating. The efficiency factor below accounts for that real-world loss.
How it works
Battery capacity
Device current draw
Usable capacity
Battery life
Usable capacity
Battery life
Frequently asked questions
How do I use the Battery Life Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.