Lithium Battery Watt Hour Calculator: (mAh / Ah ↔ Wh)

Use our lithium (LiFePO4) battery watt-hour calculator to convert the battery capacity from amp hours (Ah), or milliamp hours (mAh) to watt hours (Wh).

Lithium (LiFePO4) battery watt-hour calculator

Battery Capacity
Battery Voltage
Battery Quantity

Note: 1000 milliamp hours is equal to 1 amp.

How to use this calculator?

1 – Enter the battery capacity and select the unit type. The unit types are amp-hours (Ah), and milliamp-hours (mAh). For example, if you have a 100ah battery, enter 100 and select the unit type to Ah.

2 – Enter the battery voltage. Is this a 6v, 12v, 24v, or a 48v battery? It should be mentioned on the specs sheet of your battery or on the battery itself.

3 – Optional: Enter the number of batteries if you’re using multiple batteries. (Default value will be 1)

example: how many watt-hours are in a lithium battery?

Screenshot from the calculator: How many watt hours in a 100ah lithium battery?

100Ah lithium battery is equal to 1200 watt-hours of usable energy.

How do you calculate lithium battery watt-hours?

Multiply the battery capacity in amp-hours (Ah) by the battery voltage to calculate watt hours (Wh).

Formula: Battery capacity Watt-hours = Battery capacity Ah × Battery voltage


Let’s say you have a 12v 200ah lithium battery.

12v 200Ah battery into watt hours = 200 × 12 = 2400Wh

Lithium Battery amp-hours to Watt Hour Calculation

Here’s a chart about different capacity (Ah) lithium batteries into watt hours @ 12v, 24, and 48v.

Battery Ahwatt-hours @ 12vwatt-hours @ 24vwatt-hours @ 48v
20Ah240 Wh480 Wh960 Wh
50Ah600 Wh1200 Wh2400 Wh
70Ah840 Wh1680 Wh3360 Wh
100Ah1200 Wh2400 Wh4800 Wh
120Ah1440 Wh2880 Wh5760 Wh
150Ah1800 Wh3600 Wh7200 Wh
200Ah2400 Wh4800 Wh9600 Wh
300Ah3600 Wh7200 Wh14,400 Wh
400Ah4800 Wh9600 Wh19,200 Wh

Why calculate battery watt-hours?

Energy is equal to amp-hours multiplied by volts. Converting battery amp hours to watt-hours will give an idea of how much actual energy your battery can store or deliver.

For example, A 36v 12.8ah battery can store or deliver more energy than a 12v 30ah battery.

36v * 12.8ah = 460.8Wh
12v * 30ah = 360Wh

The benefit of converting battery amp hours to watt-hours:

  • Makes it easy to calculate the battery runtime on a specific load. The energy or power consumption for most of the appliances is mentioned in watts or watt-hours. So, converting battery capacity in watt hours will make it easy for you to estimate the battery runtime on a load.

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Chris Tsitouris is a renewable energy professional with 10+ years of experience as Director of Engineering at Solar Spectrum, previously working as Project Manager at SunPower and Energy Analyst at the National Renewable Energy Laboratory. As a thought leader, Chris has authored numerous articles and research papers.

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