Enter the harvested water (gal) and the rainfall depth (in) into the Calculator. The calculator will evaluate the Catchment Area. 

Catchment Area Formula

CA = HW / RFD / .623


  • CA is the Catchment Area (ft^2)
  • HW is the harvested water (gal)
  • RFD is the rainfall depth (in)

To calculate the Catchment Area, divide the harvested water by the rainfall depth, then divide the result by .623.

How to Calculate Catchment Area?

The following steps outline how to calculate the Catchment Area.

  1. First, determine the harvested water (gal). 
  2. Next, determine the rainfall depth (in). 
  3. Next, gather the formula from above = CA = HW / RFD / .623.
  4. Finally, calculate the Catchment Area.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

harvested water (gal) = 45

rainfall depth (in) = 34


What is Rainwater Harvesting?

Rainwater harvesting is the process of collecting, storing, and using rainwater from surfaces like roofs for various water needs, including irrigation, flushing toilets, and laundry, reducing the demand on traditional water supplies.

Why is the Catchment Area important in Rainwater Harvesting?

The catchment area is crucial because it determines the potential volume of rainwater that can be collected. A larger catchment area can capture more rainwater, making the system more efficient and providing more water for use.

How can I increase the efficiency of my Rainwater Harvesting system?

Efficiency can be increased by ensuring the catchment area is clean and unobstructed, using high-quality components for water collection and storage, and regularly maintaining the system to prevent leaks and contamination.

Are there any legal restrictions on Rainwater Harvesting?

In some areas, there may be legal restrictions or guidelines on rainwater harvesting, including permits, usage, and treatment requirements. It’s essential to check local regulations before installing a rainwater harvesting system.