Battery Life Calculator
Estimate how long a battery will last by entering its capacity in mAh and the current draw of your circuit in mA.
Estimated Runtime
—hrs
How to Use This Calculator
Find your battery's capacity (printed on the label or in the datasheet, in mAh) and measure or estimate your circuit's average current draw in milliamps. Click Calculate Runtime. Note that real-world runtime is typically 70–80% of the theoretical value due to battery efficiency, temperature, and discharge curves.
Formula
The battery life formula divides total stored charge by the rate at which it is consumed:
Time (hours) = Capacity (mAh) / Current (mA)
Example
Scenario: AA battery (2500 mAh) powering an Arduino at 30 mA average
Time = 2500 / 30
Time ≈ 83.3 hours (3 days 11 hours)
Real-world estimate at 80% efficiency: ≈ 66.7 hours
Time = 2500 / 30
Time ≈ 83.3 hours (3 days 11 hours)
Real-world estimate at 80% efficiency: ≈ 66.7 hours