How to Convert Wh to Ah: Formula and Examples

Battery capacity may be expressed in watt-hours (Wh) or amp-hours (Ah). Both are useful, but they describe different electrical quantities.

If you know a battery's watt-hour capacity and voltage, you can convert Wh to Ah with a simple formula:

Ah = Wh ÷ V

The important detail is voltage. The same amount of stored energy can correspond to very different Ah ratings at different voltages.

For the broader relationship between Wh, Ah, voltage, and battery capacity, see:

https://medium.com/@volodymyrzh/battery-capacity-explained-mah-wh-amp-hours-decoded-1dc676be5a38

The Wh to Ah Formula

Use this formula:

Amp-hours (Ah) = Watt-hours (Wh) ÷ Voltage (V)

For example, suppose a battery has:

1,200Wh
12V

The calculation is:

1,200 ÷ 12 = 100Ah

So:

1,200Wh at 12V = 100Ah

The arithmetic is simple, but the voltage cannot be ignored.

Why Voltage Changes the Ah Result

Wh measures energy, while Ah measures electrical charge.

Because these are different quantities, there is no fixed conversion such as:

1Wh = a specific number of Ah

Instead, voltage determines the relationship.

Consider a battery capacity of 1,200Wh.

At 12V:

1,200 ÷ 12 = 100Ah

At 24V:

1,200 ÷ 24 = 50Ah

At 48V:

1,200 ÷ 48 = 25Ah

All three examples represent the same 1,200Wh of nominal energy.

The Ah rating decreases as system voltage increases.

For a focused explanation of what amp-hours actually measure:

https://digitalowl.fika.bar/what-is-ah-amp-hours-explained-simply-01M2GGB34443JC68WVPZBGPX3K

Same Wh, Different Ah

This relationship is especially useful when comparing batteries used in 12V, 24V, and 48V systems.

Suppose you need approximately 2,400Wh of nominal battery energy.

You could theoretically represent that energy as:

200Ah at 12V

because:

2,400 ÷ 12 = 200Ah

Or:

100Ah at 24V

because:

2,400 ÷ 24 = 100Ah

Or:

50Ah at 48V

because:

2,400 ÷ 48 = 50Ah

The Ah numbers look very different, but the nominal energy capacity is the same.

This is why comparing Ah values without considering voltage can give a misleading impression of battery size.

Which Voltage Should You Use?

For this type of nominal capacity conversion, use the nominal voltage associated with the battery or battery system.

Do not automatically use a temporary voltage reading measured while the battery is charging or powering a load.

Real battery voltage changes with:

• State of Charge;

• battery chemistry;

• charging conditions;

• load;

• temperature;

• voltage sag.

A battery described as a 12V system will not necessarily measure exactly 12.0V throughout operation.

For capacity calculations, the manufacturer's nominal voltage provides the appropriate standardized reference in most cases.

For more detail on battery voltage:

https://digitalowl.fika.bar/what-is-voltage-battery-voltage-explained-simply-01M2GH66XEB0MHMG3Z2Y7SNBEE

Wh to Ah Conversion Examples

Here are several useful examples.

600Wh at 12V

600 ÷ 12 = 50Ah

Result: 50Ah

1,200Wh at 12V

1,200 ÷ 12 = 100Ah

Result: 100Ah

1,200Wh at 24V

1,200 ÷ 24 = 50Ah

Result: 50Ah

2,400Wh at 24V

2,400 ÷ 24 = 100Ah

Result: 100Ah

2,400Wh at 48V

2,400 ÷ 48 = 50Ah

Result: 50Ah

4,800Wh at 48V

4,800 ÷ 48 = 100Ah

Result: 100Ah

These examples make the pattern clear: the same Wh capacity requires fewer Ah as voltage increases.

Why Wh Is Useful When Comparing Battery Systems

Ah is extremely useful when working within one voltage class, but Wh provides a clearer comparison when system voltages differ.

Imagine two batteries:

Battery A: 100Ah at 12V
Battery B: 100Ah at 48V

Their Ah ratings are identical, but their nominal energy capacities are not.

Battery A:

100 × 12 = 1,200Wh

Battery B:

100 × 48 = 4,800Wh

Battery B represents four times as much nominal energy.

That is why Wh is usually the more useful number when comparing batteries across different voltage systems.

For a focused explanation of watt-hours:

https://digitalowl.fika.bar/what-is-a-watt-hour-wh-explained-simply-01M2GM471S7BVV7BQ4R37DEEAP

Does Wh ÷ V Give the Exact Usable Ah?

The formula converts nominal energy capacity into an equivalent Ah figure at a specified voltage. It does not guarantee the exact capacity available to a connected device.

Real-world usable energy can be affected by battery-management limits, temperature, discharge rate, battery age, conversion losses, and system cutoff settings.

So a battery rated at 1,200Wh and 12V can be described mathematically as 100Ah, but that does not mean every application will extract the full theoretical energy.

The conversion remains useful because it lets you translate between two common battery-capacity specifications.

The Simple Rule

To convert Wh to Ah, use:

Ah = Wh ÷ V

For example:

1,200Wh ÷ 12V = 100Ah

1,200Wh ÷ 24V = 50Ah

1,200Wh ÷ 48V = 25Ah

The stored energy remains the same. The Ah figure changes because the voltage changes.

That is the key principle: you cannot correctly convert Wh to Ah without knowing the battery voltage.