About this tool
Estimate runtime from battery capacity, voltage and device power draw. Actual runtime can vary significantly. This page explains the values requested and the method used so you can check whether the result fits your purpose.
How to use it
Enter Battery capacity, Battery voltage and Device power draw.
Press Calculate, then review the result and the method below. Use Reset to clear the values in the calculator panel.
Method used
Watt-hours = mAh ÷ 1000 × voltage. Runtime = watt-hours ÷ power draw.
Important assumptions and limits
Actual battery runtime may differ because of battery age, efficiency, temperature and changing load.
Technology note: Product labels and providers may use different definitions or rounding rules. Confirm the units used by the product or service you are comparing.
Questions about this result
Are the values I enter sent to The Decimal Space?
No. This calculator processes the values in your browser. This page does not require a calculator account or a server-side save function.
Can I use this for an important decision?
Check the inputs, units, formula and any rounding. For a decision with legal, tax, financial, medical, engineering or safety consequences, use an official source or obtain advice from an appropriately qualified professional.
Why might a result differ from another calculator?
Different tools can use different inputs, rounding, units, assumptions or formulas. Compare the calculation method rather than relying only on a displayed number.