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Technology & digital

Battery life calculator

Battery life calculator: mAh measures charge, Wh measures energy.

Your result

Complete the fields and calculate.

Calculation method and formula

Battery capacity [mAh] ÷ Average current draw [mA] × Usable capacity [%] ÷ 100

Understand the inputs

Battery capacity
Unit: mAh. Minimum 0.01. Use a measured value or your own assumption.
Average current draw
Unit: mA. Minimum 0.01. Use a measured value or your own assumption.
Usable capacity
Unit: %. Minimum 1. Maximum 100. Use a measured value or your own assumption.

Assumptions and limitations

mAh measures charge, Wh measures energy. Voltage is therefore needed for energy comparisons. Efficiency, temperature, aging and charging curves can differ from the constant model.

The formula uses the specified units. Displayed numbers are rounded; whole packs, item counts and full time periods may also be rounded within the calculation.

Worked example

Illustrative values. Replace them with your own inputs for your calculation.

Battery capacity
5000 mAh
Average current draw
500 mA
Usable capacity
90 %
Example result9 hours

Estimate at constant current draw; temperature, age and load peaks affect runtime.

Model revision: October 17, 2026 · How CleverCalc works

FAQ

Frequently asked questions

How does Battery life calculator work?+

Battery capacity [mAh] ÷ Average current draw [mA] × Usable capacity [%] ÷ 100. mAh measures charge, Wh measures energy. Voltage is therefore needed for energy comparisons. Efficiency, temperature, aging and charging curves can differ from the constant model.

What assumptions should I consider for this result?+

mAh measures charge, Wh measures energy. Voltage is therefore needed for energy comparisons. Efficiency, temperature, aging and charging curves can differ from the constant model. The formula uses the specified units. Displayed numbers are rounded; whole packs, item counts and full time periods may also be rounded within the calculation.

How accurate is the result?+

The formula uses the specified units. Displayed numbers are rounded; whole packs, item counts and full time periods may also be rounded within the calculation. Prices, measurements and model assumptions determine how well the result represents your situation.

Is this calculator free?+

Yes. Calculations and PDF export work without an account or registration.

What happens to my inputs?+

Calculations run in your browser. Results are saved locally only when you add them to My results; favourites and history are also local. Shared links contain your values. The currency tool requests the selected currencies from its rate provider without sending your amount.

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