Darcy-Weisbach Pipe Friction Loss Calculator

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

Darcy-Weisbach calculation is mobile-device-friendly as of July 11, 2014

 Solve for: Circular Duct: Enter D and V Circular Duct: Enter D and Q Non-circular Duct: Enter A, P, and V Non-circular Duct: Enter A, P, and Q Moody Friction Factor, f: Select units: Duct Length, L (ft): Use feet and seconds units Use meters and seconds units 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:

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.

LMNO Engineering, Research, and Software, Ltd.
7860 Angel Ridge Rd.   Athens, Ohio 45701  USA   Phone and fax: (740) 592-1890
LMNO@LMNOeng.com    http://www.LMNOeng.com

August 25, 2015: Made text fields show 8 significant figures rather than 16. Calculation still uses double precision internally.

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Pipe Design (Darcy-Weisbach friction losses)

Moody friction factor

Unit Conversions

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