Battery Capacity Converter
The battery capacity converter turns milliamp-hours and nominal voltage into watt-hours and estimates usable energy for a selected usable-capacity percentage.
How to use this calculator
- Enter nominal voltage, battery capacity in mAh and a usable fraction between zero and 100 percent.
- Check the units and definitions before comparing results with another source.
- Change one input at a time when comparing scenarios, and keep the reporting period and assumptions consistent.
Formula used by the battery capacity converter calculator
Energy (Wh) = voltage (V) × capacity (mAh) ÷ 1,000
- Energy (Wh) = voltage (V) × capacity (mAh) ÷ 1,000
- Watt-hours are comparable energy units, but usable output varies with discharge rate, converter losses, temperature, age and manufacturer limits.
- Inputs are checked for required values and valid ranges; displayed results are rounded for readability.
Worked examples
Worked example
A 5,000 mAh battery at 3.7 V with 85% usable energy.
Nominal capacity is 18.5 Wh; the 85% usable estimate is 15.725 Wh.
Nominal capacity is 18.5 Wh; the 85% usable estimate is 15.725 Wh.
Understanding the result
The battery capacity converter turns milliamp-hours and nominal voltage into watt-hours and estimates usable energy for a selected usable-capacity percentage.
Watt-hours are comparable energy units, but usable output varies with discharge rate, converter losses, temperature, age and manufacturer limits.
Important notes
Watt-hours are comparable energy units, but usable output varies with discharge rate, converter losses, temperature, age and manufacturer limits.
The result applies to the numbers and assumptions entered here; verify specifications for safety-critical or regulated uses.
Frequently asked questions
Why is voltage needed to convert mAh to Wh?
mAh measures electric charge, while Wh measures energy; voltage connects them through energy = voltage × amp-hours.
Can this compare batteries with different voltages?
Watt-hours can compare nominal energy more meaningfully, but real usable output and discharge limits still differ.
How do I use this calculator?
Enter nominal voltage, battery capacity in mAh and a usable fraction between zero and 100 percent.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.