Battery Life Calculator
How long will your battery last? Enter the battery capacity in mAh, voltage, and the average current draw of your device to get a realistic runtime estimate. The efficiency slider accounts for the fact that real batteries deliver less than their rated capacity.
The basic formula is:
Runtime (hours) = Battery Capacity (mAh) x Efficiency / Current Draw (mA)
Common battery capacities:
- Smartphone: 3,000-5,000 mAh
- Tablet: 5,000-10,000 mAh
- Laptop: 40-100 Wh (10,000-27,000 mAh at 3.7V)
- Power bank: 5,000-20,000 mAh
- AA battery: ~2,500 mAh (1.5V)
Real-world efficiency is typically 80-90% due to heat, voltage regulation, and battery degradation over time. Older batteries may drop to 60-70% of original capacity.