Battery Life Calculator
Calculate battery runtime from battery capacity (mAh) and device current consumption (mA).
How to Calculate Battery Life
Divide the battery capacity in milliamp-hours by the device's current draw in milliamps to estimate how long the battery will last.
Efficiency Factor
Real-world batteries rarely deliver 100% of their rated capacity. Voltage converter losses, temperature, and battery age reduce effective capacity. Use 80–90% efficiency for more realistic estimates.
Battery: 3,000 mAh, Device: 150 mA, Efficiency: 85%
Effective capacity = 3000 × 0.85 = 2,550 mAh
Runtime = 2550 / 150 = 17 hours
FAQ
What does mAh mean?
Milliamp-hours (mAh) is a unit of electric charge representing the capacity of a battery. A 3,000 mAh battery can deliver 3,000 mA for one hour, or 150 mA for 20 hours.
Why does my battery last less than calculated?
Current draw varies during use (screen brightness, wireless activity), batteries lose capacity with age, and voltage regulators consume power. Use 80–85% efficiency for realistic estimates.
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Last updated: 2026-08-08