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Swamee-Jain Friction Factor Equation and Calculator

Fluids Engineering and Design Resources

Swamee-Jain Friction Factor Equation and Calculator

This is another explicit equation for calculating the friction factor typically used in the Darcy-Weisbach. It was first presented by P. K. Swamee and A. K. Jain in 1976 in the Journal of the Hydraulics Division of ASCE. This equation is the easiest of all explicit equations for calculating the friction factor.

The Swamee-Jain equation is expressed as

Equation 1
f = 0.25 / [ log10 ( ε / 3.7 d + 5.74 / Re0.9 ) ]2


f = friction factor, (dimensionless)
ε = absolute pipe roughness, (in, mm) depends on the condition of the pipe. It ranges from 0.001 to 0.01.
d = inside diameter of pipe, (in, mm)
Re = Reyonds number, (dimensionless)



  • Piping Calculations Manual,
    E. Shashi Menon
    SYSTEK Technologies, Inc