How to use the battery life calculator
Estimate how long a battery will last. Enter battery capacity, load current, usable capacity in the fields above; the runtime, runtime are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- C — Battery capacity (mAh)
- I — Load current (mA)
- eff — Usable capacity (%)
Worked example
With battery capacity = 2000 mAh, load current = 150 mA, usable capacity = 80 %, the calculator gives runtime ≈ 10.66667 h; runtime ≈ 0.4444444 days.
Frequently asked questions
What is the formula for the battery life calculation?
Runtime (h) = C × eff / 100 / I. Runtime (days) = [Runtime] / 24. Here C is battery capacity (mAh), I is load current (mA), eff is usable capacity (%).
What inputs do I need for the battery life calculator?
You need battery capacity in mAh, load current in mA, usable capacity in %. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.