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