Rex says
The fast lane for the math you almost remember from school. Type the numbers, get the answer, move on with your day.
Try a scenario
Click to load — tweak from there.Inputs
Result
Runtime (hours)
8.00
Runtime (minutes)
480
Load current (A)
10.00
Usable energy (Wh)
960
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter battery capacity (Ah).
- 2Enter battery voltage (V).
- 3Enter load (W).
- 4Enter usable depth of discharge (%).
- 5Read your runtime (hours) on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Capacity in amp-hours divided by draw in amps gives raw hours; a depth-of-discharge limit keeps the estimate honest for lead-acid and lithium packs.
Worked example
Using the values the calculator loads with:
Inputs
- Battery capacity: 100 Ah
- Battery voltage: 12 V
- Load: 120 W
- Usable depth of discharge: 80 %
Results
- Runtime (hours): 8
- Runtime (minutes): 480
- Load current (A): 10
- Usable energy (Wh): 960
What each field means
Inputs
- Battery capacity (Ah)
- The battery capacity used in the calculation, measured in Ah. Starts at 100 Ah so you have a working example on load.
- Battery voltage (V)
- The battery voltage used in the calculation, measured in V. Starts at 12 V so you have a working example on load.
- Load (W)
- The load used in the calculation, measured in W. Starts at 120 W so you have a working example on load.
- Usable depth of discharge (%)
- The usable depth of discharge used in the calculation, measured in %. Starts at 80 % so you have a working example on load. Accepted range: 10–100 %.
Results
- Runtime (hours)
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Runtime (minutes)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Load current (A)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Usable energy (Wh)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the battery life & runtime calculator work?
Capacity in amp-hours divided by draw in amps gives raw hours; a depth-of-discharge limit keeps the estimate honest for lead-acid and lithium packs. The underlying maths is: Hours = Ah × DoD ÷ load A
What do I need to enter?
4 values: battery capacity, battery voltage, load, and usable depth of discharge. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the runtime (hours) result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Results are rounded for display; the underlying calculation keeps full precision.
Who is this tool for?
It's built for students, developers, and anyone who needs the answer right now without setting up a spreadsheet.
Accuracy and limitations
- Results are rounded for display; the underlying calculation keeps full precision.
- Very large or very small inputs may hit floating-point limits in the browser.
- Inputs outside the accepted range are clamped rather than rejected.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Battery Runtime Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/battery-runtime
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/battery-runtime" target="_blank" rel="noopener">Battery Runtime Calculator — RevenueLab</a> (2026).</p>
Source: [Battery Runtime Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/battery-runtime) (2026).