Rain Collection Calculator





Rainwater harvesting is an environmentally friendly way to conserve water. To make it easier for individuals to calculate the amount of rainwater they can collect, we’ve created an HTML Rain Collection Calculator. This calculator lets you determine the rainwater collected based on the collection area, rainfall intensity, and collection efficiency. In this guide, we’ll show you how to use the calculator, provide the formula for calculation, offer an example, address some common FAQs, and conclude with the benefits of using this tool.

How to Use

Using the Rain Collection Calculator is simple. Follow these steps:

  1. Create the HTML Form: Begin by setting up an HTML form to collect user input. Include fields for Collection Area (m²), Rainfall Intensity (mm/h), and Collection Efficiency.
  2. Add a Clickable Button: Make sure to include a clickable button within the form to trigger the calculation.
  3. Implement JavaScript: Insert JavaScript code within a <script> tag to perform the calculation when the button is clicked.
  4. Display the Result: Create an area in your HTML where the calculated rainwater collected will be displayed.


The formula to calculate the rainwater collected (RC) is as follows:

RC = A * R * C


  • RC: Rainwater Collected (in liters or any desired unit)
  • A: Collection Area (in square meters)
  • R: Rainfall Intensity (in millimeters per hour)
  • C: Collection Efficiency (expressed as a decimal or percentage)


Suppose you have a collection area of 50 m², a rainfall intensity of 10 mm/h, and a collection efficiency of 75% (0.75 as a decimal). Using the formula:

RC = 50 * 10 * 0.75 = 375 liters

So, you can collect 375 liters of rainwater in this scenario.


Q1: What is Collection Efficiency? Collection Efficiency represents the effectiveness of your rainwater collection system. It takes into account factors like runoff and losses. You can express it as a decimal (e.g., 0.75 for 75%) or a percentage (e.g., 75%).

Q2: Can I use this calculator for any unit of measurement? Yes, you can. Just make sure that all your units (area, rainfall intensity, and collection efficiency) are consistent, and the result will be in the same units.

Q3: Is it necessary to use JavaScript for the calculation? JavaScript is commonly used for interactive web calculators like this, but you can also implement the calculation logic in other programming languages if you prefer.

Q4: Can I modify the calculator’s design and style? Absolutely! You can customize the HTML and CSS to match your website’s design and style preferences.


Creating an HTML Rain Collection Calculator is a practical way to help individuals estimate the amount of rainwater they can harvest. By following the provided steps, using the formula, and implementing JavaScript, you can create a user-friendly calculator that promotes sustainable water conservation practices. Customize it to fit your needs, and encourage others to explore rainwater harvesting as an eco-friendly solution.

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