Rainfall Calculator

Created by Luciano Mino
Last updated: Nov 30, 2022

The rainfall calculator will help you calculate the total volume of rainfall that a container of known dimensions caught within a time interval.

If you don't know how to calculate rainfall, don't worry! Within a few paragraphs, you will learn how to measure rainfall at home using the volume of rainfall formula.

How to measure rainfall

Before using this precipitation calculator, let's clear one main thing. What is rainfall? By definition, rainfall is the amount of rain that falls on land during a specific period of time.

This way, if we talk about the average annual rainfall in a city, we would be referring to the amount of rain that fell on average (by measuring rainfall at different points in the city) throughout a particular year.

OK, that sounds simple enough, but how do we measure it? Since we're trying to quantify the amount of a liquid, the best way to measure it is by calculating its volume.

So, if we were to put a container and measure the volume of rainfall that it caught during, let's say, one hour, we would obtain the rainfall volume for that hour.

How to calculate rainfall at home

Therefore, to calculate rainfall, we need to find the volume of rain that fell within a container.

Suppose you want to find how much rain falls on your garden between 5 PM and 6 PM. For that, we need just three things:

  • A container, let's say a water bottle with its top cut out.
  • Its catchment area, area of the aperture of the container; and
  • The rainfall depth, which is the height reached by the water within the container.

Now we only need to calculate the volume of water contained in the bottle. Luckily, that's an effortless thing to do.

Volume of rainfall formula

We can now put the measurements in the volume of rainfall formula, which is the same as calculating the volume for any liquid (e.g. volume inside a cylinder):

V=A×hV = A \times h


  • AA is the catchment area.
  • hh water column's height. You can use any units in the volume of rainfall formula as long as you're consistent with your choice.
  • VV is the rainfall volume. Using this precipitation calculator, you can express the output in any volume unit. Just select the unit from the dropdown list next to the result.

We can also calculate the mass of this volume of water manually by multiplying it by its density!

🙋 Do you want to know if something will float or sink when placed on water? Check our water density calculator and find out!

Luciano Mino
Catchment area
Rainfall depth
Water volume
cu ft
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