Convert Watt Hours to Milliamp Hours
Watt Hours to Milliamp Hours Formula Derivation
Unit Conversion Formula Breakdown
The formula to convert watt hours to milliamp hours is mAh = (Wh × 1000) ÷ V. This is derived from the base relationship Ah = Wh ÷ V, then multiplied by 1000 to convert amp hours to milliamp hours. The "milli" prefix means one-thousandth, so 1 Ah = 1,000 mAh.
Dimensional Analysis in Energy Conversion
Using dimensional analysis: Wh has dimensions of [energy] = [power × time]. mAh has dimensions of [charge] = [current × time]. To bridge them, we divide by voltage: [energy] ÷ [voltage] = [charge]. Then we scale by 1000 to convert from Ah to mAh. This systematic approach ensures unit consistency in all battery engineering calculations. For related physics unit methods, see our chemical unit conversion guide.
Metric Prefixes Explained (milli, kilo)
Metric prefixes are fundamental to engineering: milli (m) = 10⁻³, kilo (k) = 10³, mega (M) = 10⁶. Therefore: 1 Wh = 1,000 mWh, 1 kWh = 1,000 Wh, 1 Ah = 1,000 mAh. Confusing prefixes is one of the most common conversion errors in battery specifications. Our Wh to mAh converter handles prefix conversions automatically.
Applications in IoT & Embedded Systems
Microcontroller Battery Sizing
IoT devices typically consume 10–500µA in sleep mode and 10–100mA during active transmission. A 500mAh coin cell at 3V provides 1.5Wh. If a sensor wakes every 15 minutes for 5 seconds at 50mA, daily consumption is approximately 24mAh — giving roughly 20 days of operation.
Wearable Device Energy Estimation
Smartwatches use 200–450mAh batteries at 3.8V, giving 0.76–1.71Wh. Fitness trackers use smaller cells (50–150mAh). Converting Wh to mAh helps compare devices across manufacturers who may use different rating standards. For reverse conversions, use our mAh to Wh converter.
Drone Battery Pack Calculations
Racing drones use 1300–1800mAh 4S (14.8V) LiPo batteries, providing 19.2–26.6Wh. Photography drones like the DJI Mini 4 Pro use 3850mAh at 7.38V = 28.4Wh. Converting between Wh and mAh at the correct voltage is essential for flight time estimation and regulatory compliance.
Accuracy Considerations in Energy Conversion Tools
Rounding Errors
When converting between Wh and mAh, rounding at intermediate steps can introduce significant errors. For example, 99.9Wh at 3.7V = 27,000 mAh exactly, but rounding the voltage to 3.8V gives 26,289 mAh — a 2.6% error. Always use the exact nominal voltage from the battery datasheet.
Voltage Stability Impact
Battery voltage varies during discharge: a fully charged lithium cell is 4.2V, nominal is 3.7V, and empty is 3.0V. Using nominal voltage (3.7V) for mAh calculations is standard practice, but actual delivered energy depends on the discharge curve. For complete battery formulas, visit our battery conversion calculator.