Rainwater planning tool
How much rain could your roof catch?
Get a quick estimate for a single storm or a season. Adjust the roof area and rainfall to see what might reach your storage system.
Your roof and rainfall
Use the horizontal roof footprint, not the sloped surface area.
inches
Try a storm total or a monthly/seasonal total from a local weather source.
A planning assumption for first flush, splash, leaks, and other losses.
Estimated collection
Potential water collected0 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. Actual capture depends on roof, gutters, rainfall, and system design. This is an estimate, not a water-system design.