Beyond the mAh Rating
Most people look at a battery's mAh (milliamp-hour) rating to judge its quality, but mAh alone is meaningless without knowing the Voltage. Our Advanced Battery Runtime Calculator uses Watt-hours (Wh) to give you a true estimate of your device's endurance.
The Formula: mAh to Watt-Hours
To compare batteries of different voltages, we must convert to Wh:
- Wh = (mAh / 1000) × Voltage Once we have the total energy in Wh, we simply divide by the Load (Watts) to find the runtime.
Why Batteries "Die" Faster Than Expected
If your math says 10 hours but the device dies in 7, it's usually due to two hidden factors:
- Efficiency Losses: Converters and regulators generate heat. A typical drone or laptop has a circuit efficiency of 80-90%.
- Battery Health: Lithium-ion batteries lose capacity over time. A 2-year-old battery might only have 80% "health," meaning it can only store 80% of its original charge.
- The Cutoff Voltage: Batteries don't drain to zero volts. Most devices shut down at a "cutoff voltage" (e.g., 3.2V for Li-ion) to prevent permanent damage, leaving some energy unused.
Pro-Tip: Protecting Your Battery
To maximize the lifespan of your battery, avoid frequent 100% to 0% cycles. Modern electronics last significantly longer if kept between 20% and 80% charge.