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Engineering Toolbox/Darcy Friction Factor

Pressure, Level & Process

Darcy Friction Factor

Determine the Darcy/Moody friction factor for conventional fully developed internal pipe flow from Reynolds number and relative roughness.

Friction-factor calculation

Enter actual pipe ID and the absolute roughness basis selected for the pipe condition.

The prefilled roughness is an example input only, not a material specification. Use the engineering basis appropriate to the actual pipe material and condition.

Field use

Check the factor before calculating pipe friction loss.

Useful when reviewing a Moody-chart result, validating a hydraulic worksheet, or checking whether a pressure-drop calculation is using the Darcy rather than Fanning convention.

Calculation basis

Laminar: f = 64 / Re
Turbulent: 1/√f = −2 log₁₀[(ε/D)/3.7 + 2.51/(Re√f)]

The turbulent solution is iterated from the Colebrook-White equation. The returned value is the Darcy/Moody friction factor.

Do not substitute a Fanning friction factor without conversion; the Darcy factor is four times the Fanning factor. Transitional flow is deliberately left without an automatic factor.

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