our roof size- 86 x 106 feet = 9116 sq feet
Casita is 10 x 12 = 120 sq feet,

San Anselmo & Fairfax rain fall per year = 40 inches

4000 sq roof (calculator used only goes up to 4000) produces 90% catchment: 1 inch of rain =2244 gallons, 40 inches of rain 89760 gallons

Our House-- figures doubled- 8000 sq ft roof =
1inch of rain = 4488, 40 inches of rain 179520... our house roof in a typical year will roughly catch 180,000 gallons of rainwater.

Casita figures for 100 sq ft = 1 ich of rain will catch 56 gallons, in a year will catch 2244 gallons