Rainfall Calculator

Rainfall Calculator

Catchment Area:
Catchment Area Units:
Rainfall Depth:
Rainfall Depth Units:
Answer Units:
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Rainfall Formula:

Volume = Area * Depth

Rainfall Definition

Use our Rainfall Calculator to quickly determine how much rain has fallen in your location! Knowing how much rain has fallen into your rainwater catchment system is useful when you are projecting your water harvesting capabilities.

Our calculator is also a good tool to use when you are still planning to build your rainwater catchment system. Based on the calculator’s results, you may determine that you can get by with a smaller system, or find out that you need to make it much larger to support your water harvesting needs.

Harvesting Rainwater

People have been harvesting rainwater as a means to ensure a reliable supply of water for their drinking needs, as well as for irrigation, cleaning and other vital tasks. Rainwater harvesting is more prevalent in developing nations, which often lack sufficient infrastructure to collect, sanitize and distribute water to the local citizens.

However, people are beginning to harvest rainwater in developed countries, such as in Europe and North America. It’s environmentally friendly to capture water from the sky, as it requires less energy to process than building dams and aqueducts for a thirsty population.

Using Our Rainfall Calculator

Our online Rainfall Calculator is free for anyone to use. We provide it as a service for people who need a convenient method to make rainwater harvesting calculations but who don’t have a calculator or don’t know the formula. Our calculator enables you to supply the following information about the volume, area and depth of the rainfall that you intend to measure:

  • Type in the size of the catchment area for your collected rainfall.
  • Select the catchment area units that you want to use for the calculation, such as square feet, square yards or square miles. You can also select square kilometers if you need to perform your calculation using the metric system.
  • Type in the amount of rainfall depth that you want to calculate.
  • Select the rainfall depth units, such as inches, feet or yards. You can also use metric measurements, such as millimeters or meters.
  • Choose the answer units that you want the calculator to use when it provides the results, such as cubic inches, gallons or liters.
  • Click the “Calculate” button to instantly get the answer.

Once you have made the calculations, you can print out the results to help you plan how to use your harvested rainwater. This is convenient when you don’t have access to a computer and need to share the results with one of your technicians or a customer.

Being able to capture your own rainwater is an excellent way to become more self-sufficient. If more people harvested their own water each time it rained, they could lower their water utility bills, as well as have the satisfaction and pride of doing things for themselves.

How to Calculate Rainfall

Let's be honest - sometimes the best rainfall calculator is the one that is easy to use and doesn't require us to even know what the rainfall formula is in the first place! But if you want to know the exact formula for calculating rainfall then please check out the "Formula" box above.

Add a Free Rainfall Calculator Widget to Your Site!

You can get a free online rainfall calculator for your website and you don't even have to download the rainfall calculator - you can just copy and paste! The rainfall calculator exactly as you see it above is 100% free for you to use. If you want to customize the colors, size, and more to better fit your site, then pricing starts at just $29.99 for a one time purchase. Click the "Customize" button above to learn more!