Ah to Wh Calculator – Convert Amp-Hours to Watt-Hours (Battery)

Worked examples

Example 1

100 Ah 12 V lead-acid battery

Given: 100 Ah, 12 V

E = 100 × 12

Answer: 1,200 Wh (1.2 kWh) nominal; about 600 Wh usable at 50% depth of discharge.

Example 2

100 Ah 12.8 V LiFePO4 battery

Given: 100 Ah, 12.8 V

E = 100 × 12.8

Answer: 1,280 Wh; about 1,024 Wh usable at 80%.

Example 3

200 Ah 48 V bank

Given: 200 Ah, 48 V

E = 200 × 48

Answer: 9,600 Wh (9.6 kWh).

Example 4

Reverse: 5,000 Wh at 51.2 V

Given: 5,000 Wh, 51.2 V

Ah = 5,000 ÷ 51.2

Answer: 97.7 Ah – a typical 5 kWh rack module is 100 Ah.

When you need this conversion

Battery capacity is printed in amp-hours (Ah), but amp-hours alone cannot be compared across different battery voltages. A 12 V, 24 V, and 48 V battery bank all use Ah differently, so converting to watt-hours (Wh) is the only fair way to compare storage capacity, size a battery bank against your daily energy use, or match a battery to an inverter and solar array.

The formula in plain terms

Watt-hours equal amp-hours multiplied by voltage: Wh = Ah times V. This works because power (watts) equals current (amps) multiplied by voltage, and watt-hours are simply power sustained over time. Using nominal voltage keeps the figure consistent with how manufacturers rate their batteries, even though real battery voltage shifts slightly as it charges and discharges.

Common Ah to Wh values

Ah	12 V	24 V	48 V
50 Ah	600 Wh	1,200 Wh	2,400 Wh
100 Ah	1,200 Wh	2,400 Wh	4,800 Wh
200 Ah	2,400 Wh	4,800 Wh	9,600 Wh

Practical tips

Nominal capacity is not usable capacity

The Wh figure from this formula is the battery's total nominal energy. Lead-acid batteries should not be discharged past about 50 percent depth of discharge (DoD) without shortening their lifespan, while lithium iron phosphate (LiFePO4) batteries can typically be discharged to 80-100 percent DoD. Two batteries with identical Wh ratings can deliver very different amounts of real-world usable energy.

Compare batteries on Wh, not Ah

A 100 Ah 24 V battery stores twice the energy of a 100 Ah 12 V battery. When shopping, always convert to Wh before comparing price per unit of storage.

Account for round-trip efficiency

Charging and discharging a battery is not 100 percent efficient. Lithium batteries typically run 95-98 percent efficient round trip; lead-acid batteries closer to 80-85 percent, so plan for some energy loss beyond the rated Wh.

Related tools

Frequently asked questions

How do I convert Ah to Wh?

Multiply amp-hours by voltage: Wh = Ah times V. A 100 Ah 12 V battery stores 1,200 Wh nominal.

Why do batteries need to be compared in Wh, not Ah?

Ah alone ignores voltage, so a 100 Ah 12 V battery and a 100 Ah 24 V battery store very different amounts of energy. Watt-hours account for both and let you compare batteries of different voltages fairly.

How much usable energy do I actually get from a battery?

Usable energy depends on depth of discharge: lead-acid batteries are typically limited to about 50 percent DoD, while lithium (LiFePO4) batteries can safely reach 80 to 100 percent.

Does a 24 V battery store more energy than a 12 V battery with the same Ah rating?

Yes. Doubling the voltage doubles the watt-hour capacity for the same amp-hour rating, since Wh equals Ah multiplied by V.

What voltage should I use for the calculation?

Use the battery's nominal voltage, printed on the label, not the resting or charging voltage, since nominal voltage is the standard basis manufacturers use for capacity ratings.

Ah to Wh Calculator (Amp-Hours to Watt-Hours)

Formula