Battery Life Calculator
Estimate battery runtime with a visual discharge curve chart. Select from 7 battery presets (CR2032 to LiPo), configure duty cycle mode with active/sleep phases, and adjust regulator efficiency β not just simple mAh-to-hours division. Free, no sign-up required.
Battery Capacity
Operation Mode
Advanced Options
Estimated Battery Life
Discharge Curve
What is a Battery Life Calculator?
A battery life calculator estimates how long a battery will last given its capacity in milliamp-hours (mAh) and the average current draw in milliamps (mA). It accounts for factors like regulator efficiency and battery self-discharge to provide realistic estimates for IoT devices, wearables, and embedded systems.
How to Calculate Battery Life
- Select a battery preset or enter a custom capacity in mAh
- Choose continuous mode for steady loads, or duty cycle mode for devices that alternate between active and sleep states
- Enter the current draw values for your device
- Adjust advanced options like regulator efficiency and self-discharge rate
- View the estimated battery life and discharge curve
Frequently Asked Questions
How is battery life calculated?
Battery life is calculated by dividing the effective battery capacity (mAh Γ efficiency) by the average current draw (mA). For duty cycle mode, the average current is the weighted average of active and sleep currents based on their durations.
What is duty cycle mode?
Duty cycle mode calculates battery life for devices that alternate between active (high power) and sleep (low power) states. This is common in IoT sensors, wireless devices, and embedded systems that wake periodically to take measurements or transmit data.
Why does regulator efficiency matter?
Voltage regulators (LDO or switching) waste some energy as heat. A regulator with 85% efficiency means only 85% of the battery energy reaches your circuit, reducing effective battery life by about 15%.
What is battery self-discharge?
All batteries slowly lose charge even when not in use. Typical rates are 1-3% per month for lithium batteries and 10-20% for NiMH. This becomes significant for long-duration applications.