Free energy calculator
Watt-Hours to Amp-Hours Converter
Convert stored energy in watt-hours to charge capacity in amp-hours. Voltage is required because Ah alone does not describe energy.
Calculate your estimate
Change the example values to match your system.
Estimated result
Ideal—
Typical—
Conservative—
These are estimates, not guaranteed performance.
Formula and method
Amp-hours = watt-hours ÷ volts. Milliamp-hours = amp-hours × 1,000.
Percent fields are entered as percentages; the calculation converts them to decimal fractions. Displayed results are rounded to two decimal places.
What the inputs mean
- Energy (Wh)
- Enter energy in Wh.
- Nominal voltage (V)
- Enter nominal voltage in V.
Worked example
1,200 Wh divided by 12 V equals 100 Ah (100,000 mAh).
Why the real result may differ
- Temperature, battery age, wiring resistance, and changing loads can move actual results away from the estimate.
- Manufacturer ratings may be measured under different test conditions. Measure the load when practical.
Common mistakes
- Do not confuse watts (power) with watt-hours (energy).
- Do not enter a percentage as a whole number: 90% is entered as 90 in this form and converted internally.
Frequently asked questions
Is this result guaranteed?
No. It is an engineering estimate; equipment, temperature, age, and duty cycle affect real performance.
Why are three estimates shown?
The ideal case ignores practical losses, while typical and conservative cases apply the efficiency and margin entered above.
Related tools
References
Last reviewed: August 6, 2026