Run Off Calculator


Calculating runoff is a crucial aspect of hydraulic engineering, particularly when designing drainage systems. The runoff calculator simplifies this process, providing an efficient means to determine the runoff volume. In this article, we’ll explore how to use the calculator, the underlying formula, an example scenario, frequently asked questions (FAQs), and a concluding overview.

How to Use:

Using the Run Off Calculator is straightforward. Enter the required parameters into the input fields and click the “Calculate” button. The result will display instantly, aiding engineers and planners in making informed decisions regarding drainage.


The runoff calculation involves the Rational Method formula, which is widely accepted for its accuracy:


  • Q is the runoff volume (in cubic feet per second).
  • C is the runoff coefficient (dimensionless).
  • i is the rainfall intensity (in inches per hour).
  • A is the drainage area (in acres).


Suppose we have a drainage area (A) of 10 acres, a rainfall intensity (i) of 2 inches per hour, and a runoff coefficient (C) of 0.75. Plugging these values into the formula:


Q: How accurate is the Rational Method formula?

A: The Rational Method is widely used and generally accurate for small to medium-sized drainage areas. However, for larger and more complex systems, other methods may be considered.

Q: Can the calculator handle different units?

A: Yes, as long as the units for rainfall intensity and drainage area are consistent (e.g., both in inches or both in meters).

Q: Is the calculator suitable for urban drainage planning?

A: Yes, the Run Off Calculator is versatile and applicable to various scenarios, including urban environments.


The Run Off Calculator simplifies runoff calculations, aiding engineers in designing effective drainage systems. Its user-friendly interface and adherence to the Rational Method formula make it a valuable tool in hydraulic engineering.


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