What this tool does
This tool converts electrical charge and battery capacity measurements between milliampere-hours and other common units including ampere-hours, coulombs, and ampere-seconds. Milliampere-hours (mAh) are the standard unit for expressing battery capacity in smartphones, tablets, laptops, and portable electronics. This converter helps users translate between charge units used in different contexts: mAh and Ah for battery specifications, coulombs for physics and electrochemistry, and ampere-seconds for circuit analysis. All conversions are based on the fundamental relationship that 1 ampere-hour equals 3,600 coulombs.
How it calculates
The conversion uses milliampere-hours as the base unit. The fundamental relationships are: 1 mAh = 0.001 Ah, 1 mAh = 3.6 coulombs (since 1 Ah = 3,600 C and 1 mAh = 1/1000 Ah), and 1 mAh = 3.6 ampere-seconds. For microampere-hours: 1 mAh = 1,000 μAh. The tool converts any input to mAh first, then converts to the target unit using the appropriate factor.
Who should use this
- **Electronics engineers** designing battery-powered circuits and selecting appropriate batteries - **Smartphone users** comparing battery capacities across different phone models - **Drone operators** calculating flight time based on battery capacity and motor current draw - **Physics students** converting between charge units for homework and laboratory calculations
Worked examples
Example 1: A smartphone battery is rated at 4,500 mAh. In ampere-hours: 4,500 / 1,000 = 4.5 Ah. Example 2: Converting 4,500 mAh to coulombs: 4,500 × 3.6 = 16,200 C. Example 3: A drone battery rated at 5.2 Ah converts to mAh: 5.2 × 1,000 = 5,200 mAh. Example 4: A capacitor holds 7,200 coulombs. In mAh: 7,200 / 3.6 = 2,000 mAh.
Limitations
This tool converts between charge units only and does not directly convert to energy units like watt-hours, which require knowledge of the battery voltage. Battery capacity in mAh represents total charge but not total energy, since energy depends on voltage. Actual usable capacity of batteries is typically 80-95% of rated capacity and decreases with age and temperature.
FAQs
Q: How do I convert mAh to watt-hours? A: Multiply mAh by the battery voltage and divide by 1,000. For example, 5,000 mAh at 3.7V = 5,000 × 3.7 / 1,000 = 18.5 Wh.
Q: Does higher mAh always mean longer battery life? A: Higher mAh means more stored charge, but actual battery life also depends on the device's power consumption. A 5,000 mAh battery lasts longer than a 3,000 mAh battery in the same device, but not necessarily in a different device with higher power draw.
Q: Why do power banks list both mAh and Wh? A: Airlines and regulations often use Wh for safety limits, while consumers are more familiar with mAh. A 10,000 mAh power bank at 3.7V is 37 Wh, which is well within the typical 100 Wh airline limit.
Q: What is the relationship between mAh and coulombs? A: 1 mAh = 3.6 coulombs. This comes from the definition: 1 ampere = 1 coulomb per second, and 1 hour = 3,600 seconds, so 1 Ah = 3,600 C and 1 mAh = 3.6 C.
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