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Leisure Battery Sizing Calculator

How much capacity you actually need

Quick answer

Battery Ah = (daily Ah × days between charges) ÷ usable depth of discharge. Lead/AGM give ~50% usable, lithium ~80%. Size in watt-hours first, then convert at your system voltage.

1000Wh
System voltage
Battery type
2d

Recommended capacity

230Ah

184Ah usable at 80% DoD

Daily draw

83.3Ah/day

Battery type

LiFePO4

Shop 230Ah batteries
  • Sized for 2 day(s) of use between charges at 80% usable depth of discharge.
  • Solar and/or DC-DC charging reduces the capacity you need — size for the gap between charges, not total daily use.

Affiliate disclosure: shop links are Amazon Associates links; we may earn a small commission at no extra cost to you. Guidance only — confirm against manufacturer specs before installing.

Frequently asked questions

How big a leisure battery do I need?

Work out your daily use in watt-hours, convert to amp-hours (Wh ÷ 12), multiply by how many days you want between charges, then divide by the usable depth of discharge (50% for lead/AGM, ~80% for lithium). This tool does that for you.

Why does lithium need fewer amp-hours?

Lead-acid and AGM should only be discharged to about 50% to avoid damage, so a 100Ah lead battery gives ~50Ah usable. Lithium (LiFePO4) gives ~80% usable, so you need far less nominal capacity for the same real-world use.

Do solar or a DC-DC charger change the size I need?

Yes. Battery capacity only has to bridge the gap between charges. If you drive daily or have strong solar, you can run a smaller bank than if you sit off-grid for days.

Should I size in Ah or Wh?

Size in watt-hours (energy), then convert to amp-hours at your system voltage. Wh is the honest figure because it does not change with 12V vs 24V.