Battery Life Calculator
Instantly estimate your device’s runtime and learn the science behind it.
1. Calculate Your Battery Life
Enter your battery and device details below to get an instant estimate. This tool helps you plan your projects, from simple LEDs to complex robotics.
To preserve battery health, it's recommended not to fully discharge it. 80% is a common value.
Estimated Battery Life
Enter values to see the estimate.
Discharge Visualization
This chart illustrates how the battery capacity decreases over its estimated runtime.
2. Understand the Concepts
Calculators are great, but understanding the principles behind them is even better. Explore the tabs below to become a battery expert and learn why your real-world results might differ from the estimate.
The Basic Formula
The calculation for battery life is fundamentally simple. It's the total capacity of the battery divided by the average current drawn by the device.
A Practical Example:
Let's say you have a 3000 mAh battery and your device consumes 50 mA on average.
- Convert Units: First, ensure your units are consistent. We need Amps (A) and Amp-hours (Ah).
- 3000 mAh = 3 Ah (since 1000 mAh = 1 Ah)
- 50 mA = 0.05 A (since 1000 mA = 1 A)
- Calculate: Now, apply the formula.
- 3 Ah / 0.05 A = 60 Hours
- Milliamp Hour (mAh)
- This is a measure of a battery's energy capacity. A battery with a 2000 mAh rating can theoretically provide a current of 2000mA for one hour, 1000mA for two hours, and so on.
- Current (A / mA)
- Measured in Amperes (A) or Milliamperes (mA), current is the rate at which electric charge flows. In our context, it's how much energy your device "consumes" per unit of time.
- Watt-Hour (Wh)
- Another measure of energy capacity, often used for larger batteries like those in laptops. It accounts for voltage. The formula is: Watt-Hours = (Milliamp-Hours × Volts) / 1000.
This calculator provides a theoretical estimate. In the real world, several factors can reduce the actual battery life you experience.
- Temperature: Extreme cold or heat significantly impacts a battery's chemical reactions, reducing its effective capacity and efficiency.
- Battery Age & Health: As a battery goes through charge/discharge cycles, its maximum capacity degrades. An older battery will not last as long as a new one.
- Discharge Rate: Draining a battery very quickly is less efficient and generates more heat, wasting energy. The stated mAh capacity is often based on a slow, steady discharge rate.
- Self-Discharge: All batteries slowly lose charge over time, even when not connected to a device. The rate depends on the battery chemistry and temperature.