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) | 3,500–4,500 mAh |
| Smartphone (large/flagship) | 4,500–6,000 mAh |
| Tablet (10-inch) | 7,000–10,000 mAh |
| Laptop (ultrabook) | 40–60 Wh |
| Laptop (gaming) | 60–99 Wh |
| Wireless earbuds | 40–80 mAh (per bud) |
| Smart watch | 200–400 mAh |
| E-reader | 1,500–2,000 mAh |
Typical Power Draw by Activity
| Activity | Approx Draw |
|---|---|
| Smartphone idle/standby | 5–15 mA |
| Smartphone social media | 100–200 mA |
| Smartphone video streaming | 200–400 mA |
| Smartphone gaming | 400–700 mA |
| Smartphone camera | 300–500 mA |
| Laptop light work (Word, browsing) | 8–15 W |
| Laptop video streaming | 12–20 W |
| Laptop gaming | 50–100 W |
| Tablet browsing | 2–5 W |
| Tablet video | 4–8 W |
Battery Health Degradation
Lithium-ion batteries lose capacity over charge cycles. After approximately 300–500 full charge cycles (1–2 years of daily use), a smartphone battery typically retains 80–85% 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.