Rainwater Harvesting Calculator Online

Last updated on by Editorial Staff

Rainwater Harvesting Calculator

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Quick Guide to Use the Calculator

  • Enter the total area of your roof in the “Mention Roof Area” field.
  • Select the unit of measurement for your roof area (Square Feet or Square Meters) from the dropdown.
  • Input the precipitation amount based on your location in the “Precipitation Amount” field.
  • Choose the unit for precipitation (Inches or Millimeters) from the dropdown.
  • Click the Calculate button to obtain the results in three different units.
  • To start afresh, use the Reset button.

(Note: If you mention roof area in square feet, then mention precipitation amount in inches. In the same way, if the roof area is in meters square, input precipitation amount in millimeters.)


1st one

Roof Area (ft2) X Precipitation Amount (in) X 0.623 = Amount of water Collected (gallons)

Amount of water Collected(liter) = Amount of water Collected (gallons)


Amount of water Collected (m3) = mount of water Collected (gallons) x 0.00378541

2nd one 

Roof Area (m2) X Precipitation Amount (mm) = Amount  of water Collected (liters)

Amount of water Collected  (gallons) = Amount  of water Collected (liters)

 x 0.264172

Amount of water Collected  (m3) = Amount  of water Collected (liters)


What is the Rainwater Harvesting Calculator?

The Rainwater Harvesting Calculator is a useful tool that estimates the amount of water you can collect from your roof based on its area and the precipitation amount. It provides results in different units, facilitating efficient water management.

Who Can Use This Calculator?

This calculator is designed for homeowners, businesses, and individuals interested in harnessing rainwater for various purposes.

Industries that Can Use This Calculator

  • Residential: Homeowners interested in sustainable water practices.
  • Commercial: Businesses aiming for eco-friendly initiatives.
  • Agricultural: Farms looking to optimize water resources.

Benefits of Using This Calculator

  • Water Conservation: Gauge potential rainwater harvesting to conserve water.
  • Cost Savings: Estimate potential savings on water bills.
  • Environmental Impact: Promote sustainable practices and reduce dependence on external water sources.


How accurate is the calculator?

The calculator provides estimations based on input values; accuracy may vary based on local conditions.

Can I use this for any roof type?

Yes, the calculator is versatile and applicable to various roof types.


The Rainwater Harvesting Calculator empowers users to make informed decisions about water usage and conservation.

By estimating potential collected water, individuals and industries can contribute to sustainable practices, reduce costs, and positively impact the environment.