Pipe roughness $\epsilon$ calculator

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Pipe Roughness Calculator

Absolute Roughness of Pipe Materials

Student Information

StudentCABALLERO MEDRANO

App Creation DateSeptember 10, 2026

What Is Absolute Roughness?

Absolute roughness ($\varepsilon$) is the average height of the microscopic irregularities (peaks and valleys) found on the internal surface of a pipe wall. It is an intrinsic property of the pipe material and its manufacturing process. Absolute roughness is a key input for calculating the friction factor in pipe-flow problems (e.g., using the Colebrook equation or the Moody diagram), since the ratio $\varepsilon / D$ (relative roughness) directly affects the pressure drop caused by fluid friction against the pipe wall.

How to Use This App

1. Select a pipe material from the dropdown menu below.
2. The application automatically displays the absolute roughness of the selected material.
3. Compare the resulting value in millimeters (mm), meters (m), feet (ft), and inches (in).

Select Pipe Material

-- Select a pipe material --

Absolute Roughness

Material	ε (mm)	ε (m)	ε (ft)	ε (in)
—	—	—	—	—

Mathematical Relations (Unit Conversions)

All roughness values are stored internally in millimeters (the most common unit reported by fluid-mechanics references) and converted automatically using the following relations:

$$ \varepsilon(\text{m}) = \dfrac{\varepsilon(\text{mm})}{1000} $$

$$ \varepsilon(\text{mm}) = \varepsilon(\text{m}) \times 1000 $$

$$ \varepsilon(\text{ft}) = \dfrac{\varepsilon(\text{m})}{0.3048} $$

$$ \varepsilon(\text{in}) = \dfrac{\varepsilon(\text{m})}{0.0254} $$

Base conversion factors used: 1 m = 1000 mm, 1 ft = 0.3048 m, 1 in = 0.0254 m.

Pipe Roughness Concept

The absolute roughness ε represents the average peak-to-valley height of surface irregularities on the pipe's internal wall — not the pipe's overall wall thickness.

References

• Darby, R., Chemical Engineering Fluid Mechanics, 2nd ed., Marcel Dekker, New York, 2001 (roughness table, Chapter 6, "Pipe Flow"). This textbook is the primary reference indicated for this activity.
• Transparency note on data verification: the roughness values used in this app were cross-checked against the classic pipe-roughness data set originally compiled by L. F. Moody (1944), which Darby's textbook — like most modern fluid mechanics texts — reproduces for these same materials. Because this app's author could not directly access a page scan of Darby's book to confirm exact printed digits, the values below were verified instead against multiple independent, reputable technical sources that report the same figures, listed here:
• Munson, B.R., Young, D.F., Okiishi, T.H., Fundamentals of Fluid Mechanics, 6th ed. — "Equivalent Roughness for New Pipes" table.
• White, F.M., Fluid Mechanics, 7th ed., McGraw-Hill — pipe roughness data table.
• Perry's Chemical Engineers' Handbook — pipe roughness reference values.
• Engineers Edge, "Pipe Roughness Coefficients," engineersedge.com/fluid_flow/pipe-roughness.htm — consulted for cross-verification.
• Where a source reports a range (e.g., concrete, riveted steel, wood stave) instead of a single value, this app displays the full range and uses the midpoint of that range for the numeric calculation, clearly marked as such below the results table.

Pipe Roughness Calculator — Developed by CABALLERO MEDRANO for the course Transport of Fluids. Self-contained HTML/CSS/JavaScript application. No installation required.

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