# Rain Harvesting Calculator

The rain harvesting calculator calculates the amount of rainwater that can be harvested from a given square footage of rain catchment area plus the amount of rainfall.

Catchment Area Length [A](Feet)
Catchment Area Width [B](Feet)
Rainfall (Inches)

Water Tank (Gallons)

## Building My Own Rain Harvesting System

I began planning the design of my rain-catchment system, shortly after I bought a piece of rural property that had no viable access to the public water system.

Digging a well was an option, but I heard too many stories about people who dug wells, then later, had to dig them deeper as the water supply became less available.

Since I wasn't planning to live on the property (yet), I decided that a rain catchment system would not only be fairly easy to construct, it would store the amount of water that I needed for mixing concrete and showers, etc.

On my property, I built an RV shelter that serves as a docking station for my travel trailer on weekends.  It has a 34' x 17' sheet metal roof that is perfect for a rain catchment system.

## Using the Rain Harvesting Calculator

I used the Rain Harvesting Calculator to determine how much rainwater I could capture with 1 inch of rainfall, on my 34' x 17' roof.  The result was 360.3 gallons!

## Building a Rain Harvesting System

The easiest way to harvest rainwater at your home is to add a gutter system and store the rainwater that lands on your roof into a rain barrel.  If you already have gutters installed, you are halfway there.

Cistern size should be adequate to supply your water needs during extended periods of low rainfall.

Place the water reservoir on blocks so that you can take advantage of gravity when watering your plants.

You can build a taller platform out of wood or steel to support your rain tank, you just need to make sure it is strong enough to support the tank when it is full. 360.3 gallons @ 8.34 pounds per gallon weights just over 3,000 pounds!

The pitch of the roof does not play a part in the catchment area computation.  It is the horizontal measurement between the vertical points of the roof that is calculated.

What next?