Battery Runtime Calculator
Calculate how long a battery will run a given load before it's depleted.
Calculate
Enter your values below.
Result
Estimated runtime
0
Formula used
Runtime (hours) = Battery capacity (Ah) ÷ Load current (A)
Example: 100 Ah battery with a 5 A load → runtime = 20 hours.
How to use this calculator
- Enter Battery capacity (Ah), Load current (A).
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
Does this account for battery discharge efficiency?
No, it's a simplified theoretical calculation — actual runtime is often shorter, especially at high current draws.
What if my load varies over time?
Use the average current draw for a reasonable estimate, or calculate each phase separately.
Can I use this for any battery chemistry?
Yes, the basic Ah ÷ A math applies broadly, though real-world behavior varies by chemistry (lead-acid, lithium, etc.).
How is this different from Battery Capacity Calculator?
This solves for runtime given a known capacity; the Capacity Calculator solves for capacity given a target runtime.