๐ฑ Gardening
Rain Barrel Size Calculator
A rule of thumb is that 600 square feet of roof collects about 350 gallons from one inch of rain, since a small amount is lost to splashing and evaporation. A typical downspout from a small roof can fill a 55 gallon barrel in a single decent storm.
How it works
Roof length draining to the downspout
Roof width draining to the downspout
Rainfall per storm
Annual rainfall
Loss to splashing and first flush
Barrel size
Roof catchment area
Water per inch of rain
Water from this storm
Annual collection potential
Barrels filled by this storm
Note
Frequently asked questions
How do I use the Rain Barrel Size Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.