Performing this calculation requires you to also know the depth of the area in which the water is located as you need to have cubic feet to convert to gallons.
Gallons of water per square foot of roof.
So a 50 x 20 roof is 600.
When you look at the numbers it s surprising how much water you can collect every time it rains.
Per day it would take just short of 6 days to lower the level by 1 inch.
If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.
To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above.
Take the dimensions of the footprint of your roof and convert them to inches.
So if they drain 23 million gal.
Either way you would like to know how much rain has fallen how many gallons have come down from the skies onto your roof yard block or town.
Or maybe a low pressure cell has been napping overhead and your arm is hurting from holding that umbrella while you watch your basement fill up with water.
Understanding how many gallons are within a square foot of water is useful in determining the amount of water required to fill a structure such as a pool or a pond.
The answer is about 623 gallons.
To calculate the runoff from any given rainfall.
Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water.
Rain barrel supplies list.