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Battery Life Calculator
Estimate battery runtime from capacity and load current.
Battery life
—
Estimated.
| In minutes | — |
|---|---|
| Capacity | — |
| Load | — |
| — |
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Enter your figures above to see the step-by-step working.
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How the Battery Life Calculator Works
A battery’s runtime is roughly its capacity divided by the current the device draws. Capacity in milliamp-hours (mAh) divided by load in milliamps (mA) gives hours — a 3,000 mAh battery powering a 200 mA load lasts about 15 hours in theory. Real devices lose some to heat, voltage sag and conversion inefficiency, so this applies an 85% factor for a practical estimate.
For a rough figure, keep capacity and load in matching units (mAh with mA, or Ah with A).
hours ≈ capacity (mAh) ÷ load (mA) × 0.85
Frequently Asked Questions
How long will my battery last?
Divide its capacity by the load current, then knock off about 15% for real-world losses. 3,000 mAh at 200 mA lasts roughly 12–15 hours.
What is mAh?
Milliamp-hours — a battery’s charge capacity. Higher mAh means longer runtime for the same load.
Why is real battery life shorter than the calculation?
Heat, falling voltage and inefficiency mean you never get the full theoretical runtime — hence the 85% factor.
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