Electrical units and conversion

Amp-hours to watt-hours converter

Multiply amp-hours by the pack's nominal voltage. This is the conversion that makes two batteries comparable, because watt-hours are energy and amp-hours are not.

How do you convert amp-hours to watt-hours?

Watt-hours = amp-hours × nominal voltage. A 100 Ah battery holds 1,200 Wh at 12 V, 2,400 Wh at 24 V and 5,120 Wh at 51.2 V. This is the direction that matters most in practice: a 100 Ah 12 V battery and a 100 Ah 48 V battery share a headline number while storing four times different energy, and only the watt-hour figure exposes that. The arithmetic is exact, and it describes nominal stored energy, not the energy an inverter will deliver.

Your inputs

Charge in amp-hours

Nominal voltage

Use the nominal voltage on the label, not the fully charged or resting voltage. The conversion is only as meaningful as this number.

Common voltages

1,200.0 Wh

at 12.0 V nominal

100.00 Ah × 12.0 V. Watt-hours measure energy, which is what runtime and cost calculations need.

Exact given your inputs

Watt-hours: 1,200.0 Wh
Amp-hours: 100.00 Ah
Nominal voltage: 12.0 V
Kilowatt-hours: 1.200 kWh

Round-trip check

Converting the displayed result straight back gives 100.000 Ah against an exact 100.000 Ah. The pair is exact in both directions at this voltage.

Method

Wh = Ah × V
Wh = 100.00 × 12.0 = 1,200.0000 Wh

This converter changes units. It does not tell you how much energy you can actually take out of the battery.

Assumptions

The voltage you entered is treated as the pack's nominal voltage across the whole discharge.
The conversion is pure arithmetic: no depth of discharge, inverter efficiency, temperature or discharge-rate effect is applied.
Displayed values are rounded; the arithmetic above is carried at full precision.

What can change the result?

Actual terminal voltage, which falls through the discharge and rises while charging
Chemistry: a lead-acid amp-hour rating is quoted at a slow discharge rate and shrinks at high current
Whether the label figure is nominal capacity or usable capacity

Amp-hour ratings across the common system voltages

Read across a row to see how little an amp-hour rating tells you on its own. Every figure in the row describes a battery advertised with the same number on the front.

Watt-hours = amp-hours × nominal voltage. Exact arithmetic, rounded to the nearest watt-hour for display.
Amp-hours	12 V	24 V	48 V	51.2 V
20 Ah	240 Wh	480 Wh	960 Wh	1,024 Wh
50 Ah	600 Wh	1,200 Wh	2,400 Wh	2,560 Wh
100 Ah	1,200 Wh	2,400 Wh	4,800 Wh	5,120 Wh
200 Ah	2,400 Wh	4,800 Wh	9,600 Wh	10,240 Wh
280 Ah	3,360 Wh	6,720 Wh	13,440 Wh	14,336 Wh
400 Ah	4,800 Wh	9,600 Wh	19,200 Wh	20,480 Wh

Where this conversion is used, and where it misleads

Watt-hours are the unit every downstream calculation actually wants. Runtime is watt-hours divided by load watts; cost is kilowatt-hours times a rate. Amp-hours cannot enter either formula until they have been multiplied by a voltage, which is why an amp-hour figure quoted without its voltage is not a specification at all.

The misleading part is treating the result as available energy. A 1,200 Wh lead-acid battery held to a 50% depth of discharge offers 600 Wh before you have accounted for the inverter; the same nominal figure in lithium iron phosphate at 90% depth of discharge offers 1,080 Wh. Both are still “100 Ah at 12 V”. The runtime calculator applies those losses explicitly rather than folding them into the conversion.