# Battery Runtime Calculator

> Calculate battery runtime step by step: Runtime (h) = Capacity (Ah) × Voltage (V) × DoD × Efficiency ÷ Load (W).

Page: https://freecalculator.tech/tools/battery-runtime-calculator
Last reviewed: 2026-11-03

## Formula

Runtime (h) = Capacity (Ah) × Voltage (V) × DoD × Efficiency ÷ Load (W).

- Depth of discharge and efficiency are entered by you — no chemistry is assumed.
- Percentages must be between 0 and 100.
- Load is the average power; for a varying load, use an average over the period.
- Runtime (h) = Capacity (Ah) × Voltage (V) × DoD × Efficiency ÷ Load (W).
- Inputs used: Battery capacity, Battery voltage, Load power, Usable depth of discharge, Inverter / converter efficiency.

## Inputs

- Battery capacity
- Battery voltage
- Load power
- Usable depth of discharge
- Inverter / converter efficiency

## Worked example: 12 V 100 Ah battery, 60 W load

Using 50% depth of discharge and 90% inverter efficiency.
1. Stored: 100 × 12 = 1,200 Wh.
2. Usable: 1,200 × 0.5 × 0.9 = 540 Wh.
3. Runtime: 540 ÷ 60 = 9 hours.

## Common questions

### Why is depth of discharge required?

Discharging some batteries fully shortens their life. Lead-acid is often limited to around half, while many lithium packs allow more. Use your datasheet figure.

### Does high current reduce capacity?

Yes. Lead-acid capacity drops at high discharge rates (Peukert effect). This calculator does not model that, so fast discharges will run shorter.

### What about cold weather?

Low temperatures reduce available capacity. Allow extra margin for cold conditions.

### How do I use the Battery Runtime Calculator?

Enter the required values for Battery capacity, Battery voltage, Load power, Usable depth of discharge, Inverter / converter efficiency. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

### What formula does the Battery Runtime Calculator use?

Runtime (h) = Capacity (Ah) × Voltage (V) × DoD × Efficiency ÷ Load (W). The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.

### Can the Battery Runtime Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.

## Limitations and assumptions

- No Peukert or temperature correction.
- Assumes a constant average load.
- Battery ageing reduces capacity over time.
- Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
- The result depends on the values you enter for this battery runtime calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

## Sources

- OpenStax (Rice University) — https://openstax.org/details/books/university-physics-volume-2

## Cite this page

- APA: Free Calculator. (2026, November 3). Battery Runtime Calculator. https://freecalculator.tech/tools/battery-runtime-calculator
- MLA: "Battery Runtime Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/battery-runtime-calculator.
- Link: Battery Runtime Calculator — Free Calculator, https://freecalculator.tech/tools/battery-runtime-calculator