Battery Life Calculator
Estimate runtime for any device based on battery capacity and power consumption
⚙️ Battery & Device Settings
📊 Runtime Results
0h 0min
0 hours
0 Wh
Total Capacity
0 W
Total Power
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Runtime (hours)
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Runtime (minutes)
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Runtime (seconds)
0 mA
Discharge Rate
With 80% efficiency (real-world estimate)
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Frequently Asked Questions
How do you calculate battery life?
Battery life is calculated by dividing the total energy capacity (in watt-hours) by the power consumption (in watts). For batteries rated in mAh, first convert to Wh using the formula: Wh = mAh × V ÷ 1000. Then divide by the device's power draw to get runtime in hours.
What's the difference between mAh and Wh?
mAh (milliamp-hours) measures charge capacity, while Wh (watt-hours) measures energy capacity. Wh accounts for voltage, making it more accurate for comparing batteries of different voltages. To convert: Wh = mAh × V ÷ 1000. A 5000mAh battery at 3.7V has 18.5Wh of energy.
What affects battery life?
Battery life is affected by power consumption of the device, battery capacity, voltage, ambient temperature, battery age and degradation, discharge rate (Peukert effect), device efficiency, and background processes. Real-world runtime is typically 70–85% of theoretical due to these factors.