Battery capacity in milliamp-hours (mAh) tells you how much charge a battery holds, but watt-hours (Wh) tell you how much actual energy it stores — a more useful number for comparing batteries at different voltages. Enter your Battery Capacity (mAh) and Voltage (V) into the mAh to Wh Calculator to get your battery's Energy Capacity in Wh, plus milliwatt-hours (mWh) as a secondary output.
Energy Capacity
--
Milliwatt Hours
--
To convert milliamp-hours to watt-hours, multiply the mAh value by the voltage and divide by 1000. The formula is: Wh = (mAh × V) ÷ 1000. For example, a 5000mAh battery at 3.7V equals 18.5 Wh.
mAh measures electric charge (current over time) while Wh measures energy (power over time). Since power equals voltage times current, you need the voltage to calculate the actual energy capacity of a battery.
Most smartphone batteries operate at 3.7V nominal voltage. However, check your device specifications as some newer phones may use 3.8V or other voltages for more accurate calculations.
Not necessarily. A higher mAh rating means more charge capacity, but the actual energy depends on voltage. A 3000mAh battery at 5V (15Wh) stores more energy than a 4000mAh battery at 3.7V (14.8Wh).
Battery capacity decreases in cold temperatures and may increase slightly in warm conditions. Most ratings are given at room temperature (20°C). Extreme temperatures can reduce effective capacity by 10-30%.
mAh indicates charge capacity while Wh shows actual energy storage. Power banks often list mAh at the internal battery voltage (3.7V), but output at 5V, so Wh gives a more accurate picture of usable energy.
Yes, but car batteries are typically rated in Ah (amp-hours) rather than mAh. Simply multiply the Ah rating by 1000 to get mAh, then use 12V for most car batteries in the calculator.