Darcy-Weisbach Pipe Friction Loss Calculator

Compute Major Losses (Friction Loss) in Pipes using Darcy-Weisbach Equation



Solve for: 
Moody Friction Factor, f:  
Select units:  Duct Length, L (ft):  
Duct Diameter, D (ft):  
© 2014 LMNO Engineering, Duct Area, A (ft2):  
Research, and Software, Ltd. Duct Perimeter, P (ft):  
http://www.LMNOeng.com Velocity, V (ft/s):  
Discharge, Q (ft3/s):  
Major Loss, hf (ft):  

Units in Darcy-Weisbach calculator: ft=foot, m=meter, s=second.

Darcy-Weisbach Friction Loss Equation:

Major Loss Equations

D is called the "duct diameter" to keep the terminology general to include circular pipes and non-circular pipes, also known as ducts. For rectangular pipes (ducts), D=4A/P is known as the hydraulic diameter. More information about hydraulic diameter can be found on our non-circular to circular pipe conversion page.

g = acceleration due to gravity = 32.174 ft/s2 = 9.806 m/s2.

Major loss (hf) is the energy (or head) loss (expressed in length units - think of it as energy per unit weight of fluid) due to friction between the moving fluid and the duct. It is also known as friction loss. The Darcy-Weisbach method is generally considered more accurate than the Hazen-Williams method. Additionally, the Darcy-Weisbach method is valid for any liquid or gas; Hazen-Williams is only valid for water at ordinary temperatures (40 to 75 oF). The Hazen-Williams method is very popular, especially among civil engineers, since its friction coefficient (C) is not a function of velocity or duct diameter. Hazen-Williams is simpler than Darcy-Weisbach for calculations where you are solving for flowrate, velocity, or diameter. More Discussion and References.

The Darcy-Weisbach calculation does not check for unreasonable inputs such as negative values. All values should be entered as positive.


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LMNO Engineering home page (more calculations)  

Pipe Design (Darcy-Weisbach friction losses)

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Discussion and References