mAh to Wh Calculator
Convert milliamp-hours to watt-hours at a specified battery voltage.
Interactive Electrical Calculator
mAh to Wh Calculator
Convert milliamp-hours to watt-hours at a specified battery voltage.
Result
Enter values and calculate.
About the mAh to Wh Calculator
Use the mAh to Wh Calculator below to work through battery capacity, runtime, charging time and series/parallel bank sizing in seconds, right in your browser. Convert milliamp-hours to watt-hours at a specified battery voltage. Charging time depends on charger current, battery capacity and charge efficiency together, not on any one of those numbers alone.
It's built for solar and off-grid system builders, RV and marine owners, backup-power installers, and hobbyists working with lithium or lead-acid packs, and every field updates instantly so you can try a few scenarios before committing to a real installation.
How the calculation works
Behind the scenes, the calculation follows:
Wh = (mAh × V) / 1000.
Where each input maps to a field in the calculator above:
- Capacity in mAh.
- Voltage in V.
Change any field above and the result recalculates immediately — nothing is submitted anywhere, so it's safe to experiment freely.
A worked example
For example, start with 5000 mAh for capacity and 3.7 V for voltage. Those defaults are only a starting point — replace them with your own measured or nameplate values, then press Calculate to get a result specific to your situation.
When to use the mAh to Wh Calculator
Typical reasons people reach for the mAh to Wh Calculator:
- Sizing a battery bank for a specific backup runtime target.
- Working out how long a charger will take to top up a given battery.
- Converting a battery spec sheet between Ah, Wh and mAh so it can be compared with another product.
- Planning a series/parallel wiring configuration to hit a target system voltage and capacity.
Good practice: Depth of discharge matters: a lead-acid battery rated for 100 Ah cannot safely deliver anywhere near 100 Ah of usable capacity, unlike most lithium chemistries.
Also worth knowing: Wiring batteries in series adds their voltages while capacity (Ah) stays the same as a single cell; wiring in parallel adds capacity while voltage stays the same.
Frequently asked questions
What does the mAh to Wh Calculator calculate?
Convert milliamp-hours to watt-hours at a specified battery voltage.
Can I rely on this number for a real installation?
The formula above is applied exactly to the values you enter, so the math itself is precise. Real-world results can still differ due to component tolerances, temperature, installation method, equipment efficiency and local code requirements, so treat the output as a strong planning estimate and verify final designs against manufacturer data and the electrical code that applies to your installation.
Do I need to sign up or install anything to use it?
No sign-up, download or installation is needed. The mAh to Wh Calculator runs entirely in your browser and is free to use.
Why not just estimate this instead of calculating it?
Series and parallel wiring change voltage and capacity in very different ways, and getting it backwards can damage cells or leave a system under-powered.
What should I do if the result looks off?
The mAh to Wh Calculator works on any modern browser, phone or desktop, and recalculates as soon as you press Calculate. If a result looks off, double-check that every field is filled in with the unit shown next to it (mixing up units, such as W with kW, is the most common cause of an unexpected answer) and re-enter the values.