🏠
Rainwater Tank Size Recommendation Calculator
USA-friendly units • fast results • mobile-friendly
Above the Fold
Get a simple rainwater tank size recommendation based on your target daily use and how many backup days you want. It also shows estimated monthly capture potential from your roof.
- Best for: irrigation planning, emergency backup, non‑potable household use
- Inputs: daily gallons + backup days (plus optional roof/rain)
- Outputs: recommended storage gallons
Inputs
Results
Enter values and click Calculate.
Try other Tank Calculators
📦Tank Volume / Capacity Calculator🛢️Horizontal Tank Level → Volume Calculator📊Tank Fill Percentage Calculator⏱️Tank Fill / Drain Time Calculator🔁Flow Rate Converter (GPM ↔ LPM ↔ m³/hr)🔥Propane Tank Usable Gallons Calculator⛽Fuel Tank Dipstick → Gallons Calculator🌧️Rainwater Collection Calculator (Roof → Gallons)🐠Aquarium Volume + Water Change Calculator
Below the Fold
How it works: Recommended storage ≈ daily use × backup days. We also estimate capture from roof area and average rainfall so you can sanity-check your storage choice.
Example: If you want 40 gal/day for 7 days, recommended storage starts around 280 gallons (before adjusting for capture and space).
FAQs
Should my tank match my monthly capture?
Not always. Many people size storage to their usage goal first, then adjust based on capture and budget.
What else affects tank sizing?
Local rainfall patterns, filtration, gutters, and how fast you plan to use stored water.
Is rainwater potable?
Often it’s treated as non‑potable unless filtered and disinfected appropriately. Follow local guidance.