Battery life calculator
Life (h) = capacity × usable factor ÷ average current. Enter the battery's mAh rating and the average current your device draws — including sleep and wake duty cycles — to estimate runtime in hours, days or weeks.
Device draw
Effective average current: 2 mA
Battery life
Estimated runtime
capacity × factor ÷ average current
350 h
About the estimate
A battery never delivers its full mAh rating under load — capacity falls with discharge current, temperature and age, and most devices shut down before the cell is empty. The 0.7 factor is a pragmatic IoT starting point: use 0.85 for a light, steady load and lower it for high-current or cold operation. Measure a prototype before trusting any estimate.
Building a low-power device? Find battery connectors and voltage regulators in our catalog.
Frequently asked questions
How is battery life in hours calculated?
Life in hours = capacity (mAh) × usable capacity factor ÷ average current (mA). With the defaults of a 1000 mAh battery at a 2 mA draw that is 1000 × 0.7 ÷ 2 = 350 hours, and the result can also be shown in days or weeks.
What is the usable capacity factor and why is it 0.7 by default?
The 0.7 factor accounts for capacity lost to discharge current, temperature, self-discharge and the fact that most devices stop working before the cell is truly empty. Use 0.85 for a light, steady load and a lower value for high-current or cold operation.
How do I include sleep and wake cycles in the average current?
Enter the active current in the average current field and the duty cycle as a percentage; the effective average current is current × duty ÷ 100. A sensor awake 10% of the time would enter 2 mA and a 10% duty cycle.
Estimates only — real runtime depends on chemistry, discharge rate, temperature and self-discharge. ICBOMS provides this tool for reference only.