Battery Runtime Calculator
Calculate how long a battery will last based on its capacity (mAh or Wh) and the device's power draw.
Accounts for voltage conversion losses
Enter battery capacity and current draw.
Battery Runtime Formula
Runtime (hours) = (Battery Capacity × Efficiency) / Current Draw
Runtime = (mAh × η) / mA
Runtime = (mAh × η) / mA
Example: 5000 mAh battery, 500 mA draw, 85% efficiency.
Runtime = (5000 × 0.85) / 500 = 4250 / 500 = 8.5 hours
Runtime = (5000 × 0.85) / 500 = 4250 / 500 = 8.5 hours
Common Battery Capacities
| Battery Type | Typical Capacity |
|---|---|
| AAA | 1,000 mAh |
| AA | 2,500 mAh |
| 18650 Li-ion | 2,500–3,500 mAh |
| Phone battery | 3,000–5,000 mAh |
| Power bank | 10,000–20,000 mAh |
FAQ
Why include efficiency?
Real circuits lose energy through voltage regulators, heat, and other inefficiencies. A typical efficiency of 80–90% gives a more realistic runtime estimate.
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Last updated: 2026-08-08