Battery Runtime Calculator
Calculate battery runtime with clear inputs, formula guidance, and practical result checks.
Battery Runtime measurements
Enter your values, then calculate.
Result
How to calculate battery runtime
This calculator estimates battery runtime under a specific load, accounting for system efficiency — more realistic than a simple capacity-over-current calculation since it factors in conversion losses.
How the calculation works
Runtime (hours) = (Capacity × Voltage × Efficiency) ÷ Load power. Efficiency accounts for inverter or converter losses between the battery and the actual load.
Example
A 100Ah, 12V battery at 90% efficiency powering a 100W load: Runtime = (100 × 12 × 0.90) ÷ 100 = 10.8 hours.
Frequently asked questions
How is Result calculated?
Result = [Battery capacity] × [Battery voltage] × ([Efficiency] ÷ 100) ÷ [Load power].
Is the Battery Runtime Calculator free to use?
Yes — every calculator on Simple Calculator Tools is free, runs in your browser, and does not require an account.
Battery Runtime Calculator
Runtime (hours) = (Capacity × Voltage × Efficiency) ÷ Load power. Efficiency accounts for inverter or converter losses between the battery and the actual load.
Let's understand your battery runtime result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Battery Runtime
- Include realistic system efficiency (often 85-95% for a good inverter) rather than assuming 100%, which overstates runtime.
- Real-world runtime is also affected by discharge rate and temperature, so treat this as a planning estimate, not an exact figure.
Common Battery Runtime Mistakes to Avoid
- Omitting efficiency losses entirely, which overstates achievable runtime, especially for inverter-based AC loads.
When to Use This Calculator
This calculator estimates battery runtime under a specific load, accounting for system efficiency — more realistic than a simple capacity-over-current calculation since it factors in conversion losses.