Total roof area also affects runoff.
How many gallons of rain water from gutter run off.
By this math we are able to catch about 656 66 gallons per inch of rain.
In this example 600 x 240 x 1 144 000 cubic inches of water.
A roof of 1 200 square feet in size will collect more water than one that is 600 square feet.
To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above.
Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water.
So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.
In the form below choose an area s and a rainfall amount to see how many gallons of water fell from the sky onto that area.
An inch of rain is not much but it if falls in half an hour it could flood a gutter.
Gutters and downspouts the gutters and downspouts take the rainwater down to your cistern.
Rain barrel supplies list.
Gutters and a downspout.
To calculate the runoff from any given rainfall.
The answer is about 623 gallons.