Rainfall Volume

The Rainfall Volume calculator computes the total amount of water from a reported rainfall based on the size of the land (sa) and the depth of the rainfall (D).

INSTRUCTIONS: Choose units and enter the following:⋅

• (A) Surface Area where Rain has Fallen
• (d) Rainfall Depth

Rainfall Volume (V): The calculator returns the volume in liters of water.  However this can be automatically converted to other volume units (e.g. gallons or barrels) via the pull-down menu. 

The Math / Science

The formula for the rainfall volume is:

V = A ⋅ d

where:

• V = Volume of rainfall
• A = Surface Area
• d = depth of fallen rain

Volume as a function of area is a basic math principle.  This calculator simplifies the math by performing all the appropriate unit conversions.  Most notable, is the application of acre-feet, a common water volume measurement for lakes, reservoirs and ponds.

Application

If you were to have a property of many acre size and you wanted to understand how much water fell when you had an extremely hard rain, for instance if the rainfall were reported as 2 inches of rain, then you can use this equation to compute the total water dropped on the property.

This equation computes the total volume of water falling on the surface area and reports this in gallons by default.  

Example 1:  
If for instance you had a two acre property and wondered how much rain was really there when the news reported that yesterday you had a two inch rainfall, you could input 2 ac for the surface area and 2 in for the rainfall.  

vCalc would tell you that amazingly the total water volume that fell on your property was over:  108,617 gallons

Example 2:

If you had a lake in Minnesota, the land of 10,000 lakes, and you knew that lake covered 47.5 acres and if you knew that the annual rainfall in your area was approximately 27 inches of rain each year¹, then you could compute the total water contributed to that lake over each year.  

vCalc would tell you the total annual rain contribution to the lake was approximately: 34,825,371.4285714 gallons (close to 35 million gallons!)

Hydrology (Water, Rain and Snow) Calculators:

• Snow Pack to Liquid Water Calculator
• Volume of water in snow or rain
• Weight/Mass of Snow on an Area.
• Weight of Snow on a Rectangular Area.
• Weight of Snow on a Roof.
• Weight of Snow on a Polygon Shaped Area.
• Volume of Water in a Rainfall
• Flow Rate of Broad Crested Weir
• Water Capillary Rise.
• Volume of Flood Water.
• Number of sandbags needed to build a wall or dike.
• Water Saturation Ratio
• Rain Fall Harvesting Calculator
• Peak Discharge from Drainage Basin Runoff
• Gauckler-Manning Equation
• Cipolletti Weir Flow Rate

References

1. ^ The average rainfall for Minnesota is between 19 and 35 inches