Friction Factor (Swamee-Jain) Calculator

Explicit turbulent friction factor

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Friction Factor (Swamee-Jain)

Explicit turbulent friction factor

$$f_D = \dfrac{0.25}{\left[\log_{10}\!\left(\dfrac{\varepsilon/D}{3.7}+\dfrac{5.74}{Re^{0.9}}\right)\right]^2}$$

Explicit Colebrook approximation, ~3% accuracy. Auto-switches to $f_D=64/Re$ for laminar flow.

ε (m)

D (m)

All fields required; D nonzero.

Darcy Friction Factor f_D

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