Battery Capacity Calculator
Work out how many Ah of leisure battery you need from your daily appliance load.
About the Battery capacity calculator
Use this battery capacity calculator for van leisure battery & solar setup. Work out how many Ah of leisure battery you need from your daily appliance load.
Enter your battery capacity details
From your appliance plan.
LiFePO₄ ≈ 80–90%, AGM ≈ 50%.
How it works
Daily Ah = Daily Wh ÷ Voltage. We multiply by days of reserve, then divide by the depth of discharge you can safely use to get the nominal bank size.
Round up to the next sensible cell size (25 Ah for lithium, 20 Ah for lead) for a recommended bank.
Your battery capacity results
Daily draw
125 Ah
at 12 V
Usable Ah needed
125 Ah
1 day reserve
Recommended bank
175 Ah
LiFePO₄
Why battery capacity matters for van leisure battery & solar setup
Plan with confidence
Getting your battery capacity numbers right early avoids costly rework, undersized components and surprises on the road.
Related battery & solar tools
Pair this with the rest of our battery & solar calculators to plan your full van conversion.
Battery capacity calculator FAQ
- What does the Battery Capacity Calculator do?
- Work out how many Ah of leisure battery you need from your daily appliance load. It is designed for van leisure battery and solar so you can plan with confidence.
- Is the battery capacity calculator free to use?
- Yes. All VanTools calculators, including the Battery Capacity Calculator, are free to use with no sign-up required.
- How accurate are the battery capacity results?
- Results are estimates based on the values you enter and standard van leisure battery and solar assumptions. Always sanity-check against manufacturer data and your real-world conditions.
- Can I share or save my battery capacity calculation?
- Yes. Use the Share button to copy a link that includes your inputs, or use Export to download a PDF or image of your results.