Rainwater planning tool
How much rain could your roof catch?
Your roof is a surprisingly large rain collector. Enter its footprint and a rainfall amount to get a rough idea of what could reach your tank. No buckets required.
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Your roof and rainfall
Use the roof's footprint from above, not the sloped surface area.
inches
Enter a storm total, or a monthly or seasonal amount from a local weather source.
Gutters, splash, leaks, and first-flush systems all affect this. 80% is a starting assumption.
What might make it to storage?
Estimated collection0 gallons0 liters
Before collection losses0 gal
Equivalent 55-gallon drums0
Rule of thumb: 1 inch of rain on 1 square foot of roof yields about 0.623 gallons before losses. Your gutters won't catch every drop. Water has a mind of its own. Actual capture depends on the roof, gutters, rainfall, and system design.