Flow Rate and Pressure Drop Calculator

Flow rate and pressure drop (in PSI) are fundamental concepts in fluid dynamics, specifically in the field of hydraulics. The flow rate of a fluid through a pipe and the pressure drop across that pipe are closely linked. Understanding this relationship and how to calculate pressure drop based on flow rate, viscosity of the fluid, and pipe characteristics is key in the design and operation of hydraulic systems like water supply networks, oil and gas pipelines, and many others.

Flow Rate and Pressure Drop Calculator
Flow Rate and Pressure Drop Results
Pressure drop across the pipe (in PSI) (ΔP) =

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Example Formula

To calculate the pressure drop (ΔP) in a pipe based on flow rate (Q), viscosity (μ), length (L), and radius (r), one can use the Hagen-Poiseuille equation:

ΔP = 8 × L × μ × Q / (π × r4)


  1. ΔP: Pressure drop across the pipe (in PSI).
  2. L: Length of the pipe (in feet).
  3. μ: Viscosity of the fluid (in centipoise).
  4. Q: Flow rate (in gallons per minute).
  5. r: Radius of the pipe (in inches).
  6. π: Pi, a mathematical constant approximately equal to 3.14159.

Who wrote/refined the formula

The Hagen-Poiseuille equation, which is used to calculate the pressure drop in a pipe based on flow rate, viscosity, and pipe characteristics, was derived by Gotthilf Hagen and Jean Leonard Marie Poiseuille. They independently worked on this equation during the mid-19th century. Their work continues to be foundational in fluid dynamics and hydraulics.

Real Life Application

This calculation is crucial in many engineering applications, particularly in designing and maintaining hydraulic systems. For instance, in oil and gas pipelines, calculating the pressure drop based on the flow rate and other parameters is essential to ensure the safe and efficient transport of fluids over large distances.

Key individuals in the discipline

Gotthilf Hagen and Jean Leonard Marie Poiseuille are key figures in the development of the Hagen-Poiseuille equation. Their research in the 19th century provided significant insights into fluid behavior in pipes, paving the way for more complex analyses and engineering designs.

Interesting Facts

  1. The Hagen-Poiseuille equation is crucial in industries such as oil and gas, water distribution, HVAC, and even in medical applications like intravenous fluid delivery.
  2. The application of this equation has made it possible to design efficient pipeline systems, minimizing energy losses and ensuring fluid delivery.
  3. Despite being over a century old, the Hagen-Poiseuille equation remains fundamental in fluid dynamics and continues to be used in modern engineering.


Understanding the relationship between flow rate and pressure drop is vital in the field of fluid dynamics. By utilizing the Hagen-Poiseuille equation, we can calculate the pressure drop across a pipe based on flow rate, viscosity, and pipe characteristics, leading to more efficient designs and operations of various hydraulic systems.

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