Battery Life Calculator
Estimate how long a battery will run a device from its capacity in mAh and the current the device draws. Enter battery capacity and current draw to…
8 of 8 free uses remaining today
Estimate how long a battery will run a device from its capacity in mAh and the current the device draws. Enter battery capacity and current draw to see ideal runtime and realistic runtime (80%) when you calculate.
Worked example
Example calculated from the starting values. Enter your own values and press Calculate to get your result.
With the default inputs (battery capacity = 2,000 mAh, current draw = 250 mA), the results are: ideal runtime 8.0 hours; realistic runtime (80%) 6.4 hours.
Quick reference: battery capacity vs result
Reference table based on the example values; it is not your calculation result.
| Battery capacity (mAh) | Ideal runtime | Realistic runtime (80%) |
|---|---|---|
| 1,000 | 4.0 hours | 3.2 hours |
| 2,000 | 8.0 hours | 6.4 hours |
| 4,000 | 16.0 hours | 12.8 hours |
| 10,000 | 40.0 hours | 32.0 hours |
| 20,000 | 80.0 hours | 64.0 hours |
| 40,000 | 160.0 hours | 128.0 hours |
Frequently asked questions
What formula does this calculator use?
Ideal runtime = cap ÷ load; Realistic runtime (80%) = cap ÷ load × 0.8. Variables: cap = battery capacity in mAh, load = current draw in mA.
What do I need to enter?
You need battery capacity (mAh), current draw (mA). Results update as you type.
What is an example result?
With the default inputs (battery capacity = 2,000 mAh, current draw = 250 mA), the results are: ideal runtime 8.0 hours; realistic runtime (80%) 6.4 hours.
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