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Battery Life Calculator

Battery runtime from capacity and load.

Estimate how long a battery will last from its capacity (mAh or Ah) and the load current draw, with a configurable real-world derating factor.

Daniel Oh By Daniel Oh
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

mAh
mA
%

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Hours ≈ (capacity / current) · efficiency

In depth

Estimate how long a battery will last from its capacity (mAh or Ah) and the load current draw, with a configurable real-world derating factor.