Amp-Hour Watt-Hour Calculator

Input notes

Separate nameplate capacity from measured usable capacity. Write down whether each entry is measured, rated, assumed, or calculated.

Confirm decimal placement whenever a source uses a different unit scale. A later required nominal storage decision can draw on Off-Grid Battery Bank Calculator.

Battery capacity

Default example: 100 Ah. Enter battery capacity in Ah.

Nominal voltage

Default example: 12 V. Enter nominal voltage in V.

Understanding the equation

Here, Stored energy is obtained from Wh = Ah × V. Only Battery capacity and Nominal voltage enter the numerical result.

For the example shown, stored energy equals 1,200.00 Wh. Treat that value as a demonstration, not a recommendation.

Calculate stored energy from battery capacity and nominal voltage. For pack energy, use Battery Pack Stored Energy Calculator.

Changing Battery capacity

Change Battery capacity from 100 Ah to 120 Ah while preserving the other measurements. The output changes from 1,200.00 Wh to 1,440.00 Wh.

The comparison demonstrates sensitivity, not a guaranteed field response.

Applying the result

The calculated Stored energy is meaningful only with its input conditions attached. Compare it with BMS limits, usable energy, current capability, and temperature.

A result without its source conditions is difficult to compare or audit.

Where this estimate can fail

Nominal voltage gives an energy estimate rather than an exact discharge integral.

Further engineering review can cover voltage sag, thermal rise, charge taper, and balancing. Test an additional scenario when an omitted effect has a plausible range.

Record chemistry, temperature, state of charge, age, and discharge rate.

A final reasonableness check

Begin by confirming nominal voltage at the operating point represented by the other entries. Record whether it came from a meter, nameplate, data sheet, or design assumption.

After calculating stored energy, compare its magnitude with manufacturer discharge data at the intended rate. An independent order-of-magnitude check can reveal a misplaced decimal or unit prefix.

Keep a baseline and vary the least certain measurement first. A separate analysis may be needed for chemistry-specific limits and manufacturer test conditions.

Checking the measurement basis

The calculator rejects values outside its stated field limits, but a numerically valid entry can still describe the wrong condition. Confirm battery capacity and nominal voltage against the original source before saving the result.

Use an additional case for voltage sag, thermal rise, charge taper, and balancing when that behavior is not negligible. Keep the baseline intact so the effect of each changed assumption remains visible.

Common questions before using the result