Battery Life Estimator
Estimate battery life for phones, laptops, tablets, and other devices based on usage patterns and battery capacity.
Calculate hours until next charge.
Battery life depends on three key factors: the battery’s capacity in milliamp-hours (mAh), the device’s power consumption in milliamps (mA) at a given usage level, and the battery’s age and health.
The Basic Formula
Battery Life (hours) = Battery Capacity (mAh) / Average Current Draw (mA)
Or equivalently in Watt-hours: Battery Life (hours) = Battery Energy (Wh) / Average Power (W)
Typical Battery Capacities
| Device | Typical Battery (mAh) |
|---|---|
| Smartphone (mid-range) | 3,500β4,500 mAh |
| Smartphone (large/flagship) | 4,500β6,000 mAh |
| Tablet (10-inch) | 7,000β10,000 mAh |
| Laptop (ultrabook) | 40β60 Wh |
| Laptop (gaming) | 60β99 Wh |
| Wireless earbuds | 40β80 mAh (per bud) |
| Smart watch | 200β400 mAh |
| E-reader | 1,500β2,000 mAh |
Typical Power Draw by Activity
| Activity | Approx Draw |
|---|---|
| Smartphone idle/standby | 5β15 mA |
| Smartphone social media | 100β200 mA |
| Smartphone video streaming | 200β400 mA |
| Smartphone gaming | 400β700 mA |
| Smartphone camera | 300β500 mA |
| Laptop light work (Word, browsing) | 8β15 W |
| Laptop video streaming | 12β20 W |
| Laptop gaming | 50β100 W |
| Tablet browsing | 2β5 W |
| Tablet video | 4β8 W |
Battery Health Degradation
Lithium-ion batteries lose capacity over charge cycles. After approximately 300β500 full charge cycles (1β2 years of daily use), a smartphone battery typically retains 80β85% of its original capacity. After 500+ cycles, capacity may drop to 70% or below, noticeably reducing all-day usage.
This calculator estimates usable battery life at your stated usage patterns and battery health.