Fluid Mechanics

Pipe Head Loss Calculator

Darcy-Weisbach equation with Swamee-Jain and Colebrook-White friction factor methods — plus a Decision Engine that recommends the optimal commercial pipe diameter.

Darcy-Weisbach Swamee-Jain Colebrook-White Reynolds Number

Diameter (D) m

Length (L) m

Flow Rate (Q) m³/s

Exact value: 0.020000 m³/s

Roughness (ε) mm

Exact value: 0.050000 mm

Material Preset

Calculation Method

Friction Factor

Advanced: Input Precision

Slider Step Size

Velocity

—

m/s

Reynolds Number

—

Friction Factor

—

Head Loss (H)

—

m water col.

Head Loss vs Flow Rate

Insufficient valid points for analysis

Head Loss vs Diameter

Current velocity — m/s

0 0.5 3.0 4.0+

About This Calculator

This tool calculates hydraulic head loss due to friction in a circular pipe using the Darcy-Weisbach equation, the standard method in hydraulic engineering for both laminar and turbulent flow.

The friction factor can be computed with either the Swamee-Jain explicit correlation (fast, accurate within ~2% of Colebrook for most engineering ranges) or the Colebrook-White equation (solved iteratively for higher precision).

How to Use

Set the pipe diameter and length of the analyzed segment.

Set the operating flow rate.

Choose a material preset for pipe roughness, or enter a custom value.

Pick a calculation method — Swamee-Jain for speed, Colebrook-White for iterative precision.

Review the Decision Engine panel for a recommended commercial diameter if your current sizing is suboptimal.

Understanding the Results

Reynolds Number

Ratio of inertial to viscous forces. Re < 2300: laminar. Re > 4000: turbulent. Between: transition zone.

Friction Factor

Darcy friction factor f, dependent on Reynolds number and relative roughness (ε/D).

Head Loss

Energy lost to friction, expressed as an equivalent column height of the flowing fluid.

h_f = f · (L/D) · v² / (2g)

Velocity Guidelines

Velocity	Risk
< 0.5 m/s	Sedimentation — solids may settle in the line
0.5 – 3.0 m/s	Recommended operating range
> 3.0 m/s	Erosion / excessive pressure drop

Velocity

Risk

< 0.5 m/s

Sedimentation — solids may settle in the line

0.5 – 3.0 m/s

Recommended operating range

> 3.0 m/s

Erosion / excessive pressure drop

Frequently Asked Questions

Swamee-Jain or Colebrook-White — which should I use?

Swamee-Jain is explicit and accurate within about 2% of Colebrook-White for most engineering flows (5,000 < Re < 10⁸). Use Colebrook-White when you need iterative precision or are near the transition zone.

What does the Decision Engine recommend?

It scans standard commercial pipe diameters and scores each one on energy savings (65% weight) versus relative cost increase (35% weight), then recommends the best-balanced option — only within the safe velocity range of 0.5–3.0 m/s.

Why is my head loss result different from a textbook example?

This calculator assumes water at 20°C and does not include minor losses from fittings, valves, or bends — only major (friction) losses along the pipe length.