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Watt-Hours to Milliamp-Hours Calculator

Convert watt-hours into milliamp-hours from the selected battery voltage, with supporting amp-hours and the direct mAh = (Wh × 1000) / V working equation.

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Watt-hours to milliamp-hours calculator: convert battery energy for small packs

A watt-hours to milliamp-hours calculator converts stored energy into the milliamp-hour capacity figure used on power banks, phone batteries, cameras, and compact electronics. It needs the battery's nominal voltage because the same energy total can represent very different mAh values at different voltages.

What this watt-hours to milliamp-hours calculator solves

This page converts energy in watt-hours into milliamp-hours by applying the battery's nominal voltage. It also shows the equivalent amp-hours so you can compare the same result at both the compact-electronics scale and the larger battery-bank scale.

The preset voltage list makes the most common cell and pack voltages quick to apply, while the custom entry keeps the tool flexible for uncommon systems or manufacturer-specific nominal ratings.

The milliamp-hour formula behind the result

First the calculator divides watt-hours by voltage to solve amp-hours. It then multiplies by 1,000 to express the same capacity in milliamp-hours. That means the mAh figure is not a standalone energy value. It only makes sense when paired with the voltage used for the conversion.

The exact working equation is shown beside the result so you can verify the arithmetic and confirm the voltage assumption before comparing packs from different devices or vendors.

mAh = (Wh x 1,000) / V

Use when watt-hours and nominal battery voltage are known.

Ah = mAh / 1,000

Shows the same capacity at the amp-hour scale for larger-system comparison.

Why voltage matters for mAh comparisons

Milliamp-hours can be misleading when you compare devices at different voltages. A higher-voltage pack can store the same watt-hours with fewer milliamp-hours, while a lower-voltage pack needs a larger mAh figure to represent the same energy.

That is why watt-hours are usually the better cross-device comparison unit for stored energy. The mAh result is still useful, but only after you confirm that the nominal voltage assumption is correct for the pack you are evaluating.

What this conversion does not model

This calculator does not estimate runtime, charger losses, regulator losses, discharge curves, usable depth of discharge, or temperature-related capacity changes. It is a static conversion from rated energy to rated capacity.

Use it as a planning and comparison aid. For real-world battery behaviour, confirm the result against datasheets, measured runtime, and the actual device power path.

Frequently asked questions

Why can two devices with the same watt-hours show different mAh values?

Because milliamp-hours depend on nominal voltage. The same energy total produces a different mAh figure at 3.7 V than it does at 5 V or 12 V.

 Is watt-hours or milliamp-hours better for comparing batteries?

Watt-hours is the better cross-device comparison because it measures energy directly. Milliamp-hours is useful only when the compared packs use the same nominal voltage.

 Should I use this result as a runtime estimate?

No. Runtime also depends on device power draw, efficiency losses, cutoff voltage, temperature, and battery ageing. This page converts rated capacity only.

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