Pressure Drop Calculator

Pipe pressure drop calculator. Laminar flow, horizontal pipe  
Flow Rate, Q (m3/s): 
Pipe Inside Diameter, D (m): 
Pipe Length, L (m): 
Density, ρ (kg/m3): 
Dynamic Viscosity, μ (N-s/m2): 
Pressure Drop, P1-P2 (N/m2): 
Velocity, V(m/s): 
Reynolds Number, Re: 

Pipe Pressure Drop Drawing and Equation:

Pressure drop drawing

Pressure drop equation

Pipe Pressure Drop Equation Derivation

For steady flow of an incompressible fluid in a constant diameter horizontal pipe using the Darcy-Weisbach friction loss equation, the energy equation from location 1 to 2 is expressed in terms of pressure drop as:

Pressure drop energy equation


Area, velocity, Reynolds number for pressure drop derivation

When Re < 2100, flow is laminar and:

Friction factor for pressure drop derivation

Then pressure drop is:

Equation 1 for pressure drop   Equation 2 for pressure drop

The final pressure drop equation is often called Poiseuille's law after the original researcher (Munson et al., 1998, p. 468).

Unit abbreviations, symbols: kg=kilogram, m=meter, N=Newton, s=second. A=Pipe area, f=Moody friction factor.

Reference for pressure drop: Munson, B. R. Young, D. F. and Okiishi, T. H. 1998. Fundamentals of Fluid Mechanics. John Wiley and Sons. Inc. 3ed.


© 2017-2024 LMNO Engineering, Research, and Software, Ltd.  All rights reserved.

Please contact us for consulting or questions about pressure drop.

LMNO Engineering, Research, and Software, Ltd.
7860 Angel Ridge Rd.   Athens, Ohio 45701  USA   Phone: (740) 707-2614


LMNO Engineering home page (full list of calculators)  

Calculator with more units, built-in liquid and gas properties, laminar, turbulent

Unit Conversions