Use our conversion calculator to easily convert milliamp hours to watt hours (mAh to Wh).
Or would you rather convert watt hours to milliamp hours?
Milliamp Hours to Watt Hours Conversion Chart
Here's a chart converting milliamp hours to watt hours at 3.7 volts -- the most common voltage for the small lithium batteries found in portable devices such as phones, tablets, battery packs, and Bluetooth speakers.
|Milliamp Hours (mAh)
|Watt Hours (Wh)
How to Convert Milliamp Hours to Watt Hours (mAh to Wh)
To convert milliamp hours to watt hours, multiply milliamp hours by volts then divide by 1,000.
Formula: watt hours = milliamp hours × volts ÷ 1,000
Abbreviated formula: Wh = mAh × V ÷ 1,000
Phone battery capacities are often given in milliamp hours. For instance, my iPhone XR has a 2,942mAh battery.
To figure out its battery capacity in watt hours, we need to know the battery voltage. Most smartphones, including iPhones, use a lithium-ion battery with a nominal voltage of 3.7 volts. We’ll use that as our voltage.
With all the necessary info, we can convert milliamp hours to watt hours by plugging in to the above equation.
2,942mAh × 3.7V ÷ 1,000 = 10.8854Wh
So, my iPhone XR has a battery capacity of about 10.9Wh.
Why Convert Milliamp Hours to Watt Hours?
Most often, converting milliamp hours to watt hours is useful for comparing the battery capacity of batteries with different voltages.
The total energy a battery can deliver in watt hours depends on its milliamp hours and voltage. So, if you have batteries with different voltages, looking at their amp hour or milliamp hour capacity alone can be misleading.
For example, consider the following 2 batteries:
- Battery A is a 10,000mAh 3.7V battery
- Battery B is a 10,000mAh 12V battery
If you only look at their milliamp hour capacity, you’d assume both batteries store the same amount of energy. However, because their voltages are different, we need to calculate their watt hours to be able to accurately compare them.
Battery A: 10,000mAh × 3.7V ÷ 1,000 = 37Wh Battery B: 10,000mAh × 12V ÷ 1,000 = 120Wh
Now that we know the watt hours of both batteries, we can see that Battery B can deliver nearly 4 times as much energy as Battery A.
Another important reason to calculate a battery’s watt hours is to estimate how long it'll be able to power your devices. Most electronics and appliances list their energy consumption in watts (W), and you can do a quick and dirty estimate of battery runtime by dividing watt hours by watts.
To illustrate, let's say you're using a 30,000mAh 3.7V portable battery to power a 10W camping lantern. To estimate how long you'll be able to run your lantern, you first need to calculate the battery's watt hours.
30,000mAh × 3.7V ÷ 1,000 = 111Wh
Now that you know its watt hours, you can estimate its runtime by doing the following calculation:
111Wh ÷ 10W = 11.1 hrs
Your battery will be able to power your camping lantern for around 11 hours before needing to be recharged. You wouldn't have been able to estimate the runtime had you not converted milliamp hours to watt hours.
Note: Like I said, this is a quick and dirty way to estimate battery runtime. In reality, there are a number of factors that affect how long a battery will last.
How to Convert Watt Hours to Milliamp Hours (Wh to mAh)
Sometimes, your device's battery capacity may be given in watt hours and you'll want to calculate its milliamp hour capacity. To convert watt hours to milliamp hours, divide watt hours by volts then multiply by 1,000.
Formula: milliamp hours = watt hours ÷ volts × 1,000
Abbreviated formula: mAh = Wh ÷ V × 1,000
Let’s say you have a 45Wh portable battery charger, and you want to know its battery capacity in milliamp hours. You look in the product manual and see that the battery voltage is 3.7 volts. With that info, you can calculate its milliamp hours by doing the following calculation:
45Wh ÷ 3.7V × 1,000 = 12,162.16
So, in this example, your portable charger has a 12,162mAh battery. If your phone has a battery capacity of 4,000mAh, then you can expect to get around 3 phone charges out of your portable charger. (Though, in practice, usable battery capacity varies based on a range of real-world factors including discharge rate and battery age.)
How to Convert Amp Hours to Watt Hours (Ah to Wh)
Larger batteries with higher voltages -- such as 12V and 24V batteries -- usually list their capacity in amp hours. 1 amp hour is equal to 1,000 milliamp hours, like how 1 meter is equal to 1,000 millimeters.
To convert amp hours to watt hours, simply multiply amp hours by volts.
Formula: watt hours = amp hours × volts
Abbreviated formula: Wh = Ah × V
Calculator: Amp Hours to Watt Hours Calculator
Let's say you have a 12V 100Ah lithium iron phosphate (LiFePO4) battery.
You know its battery capacity is 100Ah and its voltage is 12V, so here's how you calculate its watt hours:
100Ah × 12V = 1,200Wh
Turns out your LiFePO4 battery has a capacity of 1,200 watt hours.
Note: You may notice on the battery label that it claims to have 1,280 watt hours. This is because the brand uses a voltage of 12.8 volts in their calculation, which is more reflective of the operating voltage of this type of rechargeable battery.
How to Convert Milliamp Hours to Kilowatt Hours (mAh to kWh)
Because the units are orders of magnitude different (consider millimeters compared to kilometers), you'll rarely need to convert milliamp hours to kilowatt hours.
But if you need to, you do so by multiplying milliamp hours by volts and then dividing by 1,000,000.
Formula: kilowatt hours = milliamp hours × volts ÷ 1,000,000
Abbreviated formula: kWh = mAh × V ÷ 1,000,000
Let’s say you have a 20,000mAh 3.7V battery pack. Here’s how to convert its milliamp hours to kilowatt hours.
20,000mAh × 3.7V ÷ 1,000,000 = 0.074kWh
Your battery pack as a capacity of 0.074kWh. For reference, the average US household uses around 30kWh of electricity per day!