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Friction Factor Calculator

Compare Colebrook, Haaland, and Swamee-Jain turbulent friction-factor methods with laminar and transitional warnings.

Friction Factor inputs

Result section

warningColebrook-White bounded iterative solution

Darcy friction factor

0.022174536

Secondary results

Fanning friction factor: 0.005543634
Reynolds number: 100,000
Relative roughness: 0.001
Colebrook iterations: 39

Unit conversion summary

Unit-normalization summary: 100,000; 0.001

Warnings

Calculations are performed locally in your browser and are not submitted to a third-party calculation API.
Fluid presets are starter values only; verify properties at the actual operating condition.

Assumptions

Darcy friction factor is reported as the primary result.
Pipe-flow correlations are approximate and correlation-dependent.

Calculation steps

Classify Reynolds numberTurbulent method
Calculate Darcy friction factor0.022174536
Convert to Fanning factor0.005543634

Darcy friction factor method

1 / \sqrt{f_D} = -2\log_{10}(\epsilon/(3.7D_h)+2.51/(Re\sqrt{f_D}))

Colebrook-White bounded iterative solution

Re = 100,000

epsilon / D_h = 0.001

Method comparison table

CFD result comparison table
Quantity	Value
Colebrook Darcy f	0.022174536
Haaland Darcy f	0.021966214
Swamee-Jain Darcy f	0.022342412

Technical visual

Technical sketch for friction factor calculator. Values are illustrative; calculated values appear in the result section.

Engineering interpretation

Turbulent and transitional friction factors depend on roughness and selected correlation.

What is the friction factor calculator?

Calculate Darcy friction factor for pipe-flow pressure-loss estimates using direct Reynolds/roughness inputs or coupled CFD flow inputs.

How to use the friction factor calculator

Select the calculation mode that matches the data you already have.
Enter values with units; the calculator normalizes inputs to SI internally.
Review derived values, warnings, formulas, and assumptions before using the result in another CFD step.
Use the Darcy friction factor in the Pressure Drop or Y Plus calculators.

Input explanations

Geometry inputs are used to derive hydraulic diameter, cross-sectional area, or characteristic length where needed.
Flow input modes derive velocity from direct velocity, volumetric flow rate, or mass flow rate when applicable.
Dynamic viscosity uses density to derive kinematic viscosity; kinematic viscosity can be used directly where density is mathematically unnecessary.
Fluid presets are starter values only and can be overridden manually.

Notation

Formula notation
Symbol	Meaning	Unit
f_D	Darcy friction factor	dimensionless
f_F	Fanning friction factor	dimensionless
Re	Reynolds number	dimensionless
epsilon/D_h	Relative roughness	dimensionless

Worked examples

Laminar: Re = 1000 gives Darcy f_D = 0.064.

Smooth turbulent: Re = 100000 and epsilon/D = 0 gives Colebrook f_D about 0.01799.

Rough turbulent: Re = 100000 and epsilon/D = 0.001 gives Colebrook f_D about 0.02217.

Cross-tool workflow

The Friction Factor Calculator reports Darcy friction factor as the primary value and clearly distinguishes Fanning friction factor.

Use friction factor in Pressure Drop Calculator Use friction factor in Y Plus Calculator

Common mistakes

Confusing Darcy friction factor with Fanning friction factor.
Entering absolute roughness as relative roughness.
Ignoring transitional-flow uncertainty.
Using turbulent correlations below their valid range.

Limitations

Colebrook, Haaland, and Swamee-Jain are pipe-flow correlations and are not universal CFD closure models.
Transitional-flow results are uncertain.
Very rough or unusual surfaces may fall outside supported correlation assumptions.

References

White Fluid Mechanics: White, F. M., Fluid Mechanics, McGraw-Hill.
Fox and McDonald Fluid Mechanics: Fox, McDonald, and Pritchard, Introduction to Fluid Mechanics, Wiley.
Versteeg and Malalasekera CFD: Versteeg, H. K. and Malalasekera, W., An Introduction to Computational Fluid Dynamics, Pearson.
Pope Turbulent Flows: Pope, S. B., Turbulent Flows, Cambridge University Press.
NASA Turbulence Modeling Resource: NASA Langley Research Center, Turbulence Modeling Resource.

What is the Darcy friction factor?

It is the dimensionless factor used in the Darcy-Weisbach pressure-loss equation.

Darcy versus Fanning?

The Fanning friction factor is one quarter of the Darcy friction factor: f_F = f_D / 4.

What is relative roughness?

Relative roughness is absolute roughness divided by hydraulic diameter.

Why is Colebrook iterative?

The Colebrook equation contains f_D on both sides, so it must be solved numerically.

What happens in transitional flow?

Results are uncertain and should be treated as educational estimates, not a universal design value.

Can I compare methods?

Yes. Comparison mode shows Colebrook, Haaland, and Swamee-Jain values where applicable.

Does this create a Moody chart?

No. It computes selected values and comparisons without building a full chart application.

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Engineering disclaimer

This tool is intended for educational, estimation, and preliminary CFD setup support. Always verify critical engineering calculations with applicable standards, validated software, solver documentation, and qualified professional judgment.

Need Professional Support?

ScholarTool is powered by ScholarEase Consultancy Services LLP. Professional engineering, simulation, research, and technical documentation support is available through the connected services website.

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Last reviewed: 2026-06-19

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Friction Factor inputs

Result section

warningColebrook-White bounded iterative solution

Darcy friction factor

0.022174536

Secondary results

Fanning friction factor: 0.005543634
Reynolds number: 100,000
Relative roughness: 0.001
Colebrook iterations: 39

Unit conversion summary

Unit-normalization summary: 100,000; 0.001

Warnings

Calculations are performed locally in your browser and are not submitted to a third-party calculation API.
Fluid presets are starter values only; verify properties at the actual operating condition.

Assumptions

Darcy friction factor is reported as the primary result.
Pipe-flow correlations are approximate and correlation-dependent.

Calculation steps

Classify Reynolds numberTurbulent method
Calculate Darcy friction factor0.022174536
Convert to Fanning factor0.005543634

Darcy friction factor method

1 / \sqrt{f_D} = -2\log_{10}(\epsilon/(3.7D_h)+2.51/(Re\sqrt{f_D}))

Colebrook-White bounded iterative solution

Re = 100,000

epsilon / D_h = 0.001

Method comparison table

CFD result comparison table
Quantity	Value
Colebrook Darcy f	0.022174536
Haaland Darcy f	0.021966214
Swamee-Jain Darcy f	0.022342412

How to use the friction factor calculator

Select the calculation mode that matches the data you already have.
Enter values with units; the calculator normalizes inputs to SI internally.
Review derived values, warnings, formulas, and assumptions before using the result in another CFD step.
Use the Darcy friction factor in the Pressure Drop or Y Plus calculators.

Input explanations

Geometry inputs are used to derive hydraulic diameter, cross-sectional area, or characteristic length where needed.
Flow input modes derive velocity from direct velocity, volumetric flow rate, or mass flow rate when applicable.
Dynamic viscosity uses density to derive kinematic viscosity; kinematic viscosity can be used directly where density is mathematically unnecessary.
Fluid presets are starter values only and can be overridden manually.

Symbol

Meaning

Unit

f_D

Darcy friction factor

dimensionless

f_F

Fanning friction factor

dimensionless

Reynolds number

dimensionless

epsilon/D_h

Relative roughness

dimensionless

References

White Fluid Mechanics: White, F. M., Fluid Mechanics, McGraw-Hill.

Fox and McDonald Fluid Mechanics: Fox, McDonald, and Pritchard, Introduction to Fluid Mechanics, Wiley.

Versteeg and Malalasekera CFD: Versteeg, H. K. and Malalasekera, W., An Introduction to Computational Fluid Dynamics, Pearson.

Pope Turbulent Flows: Pope, S. B., Turbulent Flows, Cambridge University Press.

NASA Turbulence Modeling Resource: NASA Langley Research Center, Turbulence Modeling Resource.

Friction Factor inputs

Friction factor

Result section

Secondary results

Unit conversion summary

Warnings

Assumptions

Calculation steps

Darcy friction factor method

Method comparison table

Technical visual

Engineering interpretation

What is the friction factor calculator?

How to use the friction factor calculator

Input explanations

Notation

Worked examples

Cross-tool workflow

Common mistakes

Limitations

References

Related tools

Professional support from ScholarEase Consultancy Services LLP

Print summary

Engineering disclaimer

Need Professional Support?

Friction Factor inputs

Friction factor

Result section

Secondary results

Unit conversion summary

Warnings

Assumptions

Calculation steps

Darcy friction factor method

Method comparison table

Technical visual

Engineering interpretation

What is the friction factor calculator?

How to use the friction factor calculator

Input explanations

Notation

Worked examples

Cross-tool workflow

Common mistakes

Limitations

References

Related tools

Professional support from ScholarEase Consultancy Services LLP

Print summary

Engineering disclaimer

Need Professional Support?