Battery Life Calculator - Estimate Device Runtime

• Avoid full discharges. Lithium batteries last longer when kept between 20–80% charge. Deep cycling accelerates capacity loss.
• Reduce screen brightness. The display is the single largest power consumer in most mobile devices — cutting brightness 30% can extend runtime 15–20%.
• Disable background refresh. Apps syncing in the background can consume 10–25% of battery without you noticing. Enable it only for critical apps.
• Mind the temperature. Batteries discharge faster in cold and degrade faster in heat. Ideal operating range is 15–25°C (59–77°F).
• Use low-power or airplane mode. Radio transmitters (Wi-Fi, LTE, Bluetooth) are heavy consumers. Disable unused radios for a significant runtime boost.
• Slow-charge when possible. Fast charging generates heat, which degrades battery cells over time. Overnight slow-charging extends overall battery lifespan.
• Match charger to device. Using an underpowered or overpowered charger reduces efficiency and can stress cells. Always use the manufacturer-recommended output.
• Store at 50% for long-term. If storing a device unused for weeks or months, keep it at around 50% charge in a cool, dry place.

The core formula is straightforward:

Runtime (hours) = (Capacity in mAh × Efficiency) ÷ Current Draw (mA)

Or, using watt-hours:

Runtime (hours) = (Capacity in mAh × Voltage × Efficiency) ÷ Power (W) ÷ 1000

The efficiency factor accounts for real-world losses: heat generation in battery cells, voltage conversion losses in the device's power management IC, and the fact that batteries cannot fully discharge to rated capacity under load. A value of 85% is a good general estimate for lithium-ion cells; older or colder batteries may warrant 70–75%.