how to convert rain to gallon collected

I have a cistern that is connected to our roof.
If an 1" of rain fall on my roof and the roof size is 52 feet by 52 feet, how many gallons of water does that convert to? :?
If we get a good shower that passes by, I can get an idea of how much water was collected.

Thanks.

chrisusvi

I have a cistern that is connected to our roof.
If an 1" of rain fall on my roof and the roof size is 52 feet by 52 feet, how many gallons of water does that convert to? :?
If we get a good shower that passes by, I can get an idea of how much water was collected.

Chrisusvi:

If the measurements for your roof are horizontal (not pitched) and ALL of the water from the roof is collected, calculate the ft3 (cubic feet) of roof area and inches of rain and multiply by 7.48052 gal/ft3

(1"/12") x 52 ft x 52 ft = 0.08333 ft x 52 ft x 52 ft = 225.32432 ft3

225.32432 ft3 x 7.48052 gal/ft3 = 1,685.5 gallons

I forgot about the roof pitch. The roof's pitch is about 5 10 or 5 12 pitch.