A watt hour to amp hour calculator converts energy measured in watt-hours (Wh) into charge capacity measured in amp-hours (Ah) by dividing by voltage. This simple conversion is essential when comparing batteries, sizing solar systems, checking power banks, or estimating runtime for DC devices. Think about it: because Wh represents total energy while Ah represents charge flow, the voltage of the battery or system must always be included. Without the correct voltage, a conversion can be misleading, especially when moving between 12 V, 24 V, 48 V, or low-voltage lithium packs.
Introduction
Battery specifications are often written in different units, which can make comparison confusing. But one battery may list 100 Wh, another may list 8 Ah, and a third may show 12 V 10 Ah. A watt hour to amp hour calculator helps bridge these differences by showing how much charge a battery can deliver at a given voltage.
This conversion is especially useful for:
- Solar power systems that store energy in DC batteries
- RV, marine, and off-grid applications where voltage systems vary
- Power banks and portable electronics that use lithium cells
- UPS systems where runtime depends on stored energy
- DIY projects that require matching batteries to loads
The key idea is that watt-hours measure energy, while amp-hours measure charge. Voltage is the link between the two And that's really what it comes down to. And it works..
What Are Watt-Hours and Amp-Hours?
Watt-Hours (Wh)
A watt-hour is a unit of energy. Practically speaking, it tells you how much work a battery can perform over time. To give you an idea, a 100 Wh battery can deliver 100 watts for one hour, 50 watts for two hours, or 10 watts for ten hours, assuming ideal conditions.
Watt-hours are useful because they account for both voltage and current. That
makes Wh a more consistent measure for comparing batteries of different voltages. A 100 Wh battery at 12 V and a 100 Wh battery at 24 V store the same amount of energy, but their charge ratings in amp-hours will differ. That is why voltage is not optional when converting between the two units Not complicated — just consistent..
The official docs gloss over this. That's a mistake Most people skip this — try not to..
Amp-Hours (Ah)
An amp-hour is a unit of electric charge. It describes how much current a battery can deliver over a one-hour period. Here's one way to look at it: a 10 Ah battery can theoretically supply 10 A for one hour, 5 A for two hours, or 1 A for ten hours.
Amp-hours are common in battery labeling because they describe the charge available from a battery at a particular voltage. Even so, two batteries with the same Ah rating can contain very different amounts of usable energy if their voltages are different.
For example:
- A 12 V 10 Ah battery stores 120 Wh
- A 48 V 10 Ah battery stores 480 Wh
Even though both are rated at 10 Ah, the 48 V battery contains four times as much energy.
The Conversion Formula
The relationship between watt-hours, amp-hours, and voltage is straightforward:
Ah = Wh ÷ V
Where:
- Ah = amp-hours
- Wh = watt-hours
