Battery Runtime Calculator
Fill in the values and the answer updates as you type.
How the Battery Runtime Calculator works
Usable energy (Wh) = Ah × volts × depth of discharge × inverter efficiency. Runtime = usable energy ÷ load watts. Lead-acid batteries are usually limited to about 50% depth of discharge, lithium to 80–90%. Cold weather and old cells reduce real runtime. Example: with the default values, runtime comes to 2.9 hours.
Inputs and results
The Battery Runtime Calculator takes 5 inputs and gives 3 results.
What you enter
- Battery capacity (Ah) — starts at 100.
- Battery voltage (V) — starts at 12.
- Load power (W) — starts at 300.
- Usable depth of discharge (%) — starts at 80.
- Inverter efficiency (%) — starts at 90.
What you get
- Runtime (hours)
- Runtime (minutes)
- Usable energy (Wh)
Example: Battery Runtime Calculator with the starting values
With battery capacity 100 Ah, battery voltage 12 V, load power 300 W, usable depth of discharge 80 % and inverter efficiency 90 %, the calculator returns:
| Runtime (hours) | 2.9 |
|---|---|
| Runtime (minutes) | 173 |
| Usable energy (Wh) | 864 |
Change any value above and the results update straight away.
Battery Runtime Calculator FAQ
How do I use the Battery Runtime Calculator?
Enter battery capacity, battery voltage, load power and usable depth of discharge in the fields, then read runtime (hours), runtime (minutes) and usable energy (wh) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Battery Runtime Calculator calculate?
How long a battery can power a load. It returns runtime (hours), runtime (minutes) and usable energy (wh) from the 5 values you provide.
What values does the Battery Runtime Calculator start with?
It opens with battery capacity 100 Ah, battery voltage 12 V, load power 300 W and usable depth of discharge 80 % so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Battery Runtime Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Battery Runtime Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.