Battery Life Calculator
Estimate runtime from battery capacity and load. Results are approximate; real runtime depends on temperature, aging, discharge rate, etc.
Quick Device Presets
Click to fill typical parameters for fast estimation (average values for reference only).
Voltage may be optional/required depending on capacity unit and load mode.
Manual copy (fallback)
Copy or download as TXT.
Typical Power of Common Devices
| Device | Typical Battery | Typical Power | Notes |
|---|---|---|---|
| Smartphone | 4000–6000 mAh | Idle 0.5–1.5 W; active 2–5 W | Depends on brightness, radio and app load |
| Laptop | 40–80 Wh | Web/office 10–30 W; heavy 30–60 W | CPU/GPU load and brightness matter; gaming/compile higher |
| Tablet | 6000–10000 mAh | Typical 2–6 W | Screen size and brightness dependent |
| Bluetooth earbuds | buds 40–80 mAh; case 300–600 mAh | 20–80 mW | Volume, codec and link quality affect draw |
| Smartwatch | 200–600 mAh | 50–200 mW | Always‑on display, HR/GPS increase power |
| Electric toothbrush | 600–1200 mAh | 1–2 W (active) | Only during operation; standby is very low |
| Wireless mouse | 300–800 mAh | 5–20 mW | Higher while moving/wake |
| Wireless keyboard | 1000–3000 mAh | 10–50 mW | Backlight raises draw notably |
| Electric shaver | 600–2000 mAh | 3–8 W (active) | Varies by speed/torque mode |
Notes
- Current mode: hours ≈ capacity (Ah) ÷ current (A) × usable × efficiency.
- Power mode: hours ≈ energy (Wh) ÷ power (W) × usable × efficiency.
- If using DC-DC converters, set “system efficiency” to the real conversion efficiency (e.g., 85%–95%).
Battery Capacity Units & Conversion
- 1000 mAh = 1 Ah; mAh measures charge and is common for small devices.
- Wh = Ah × V; mWh = mAh × V; Wh measures energy and compares across voltages.
- Converting mAh ↔ Wh requires voltage; use nominal voltage as an approximation.
- Series increases voltage with same Ah; parallel increases Ah with same voltage.
- Real runtime varies with temperature, aging, discharge rate and losses; conversions are approximate.
