Friction Loss Calculator
Calculate pipe friction loss and pressure drop using Darcy-Weisbach, Hazen-Williams, or Manning equations. Supports multiple fluids, temperatures, pipe materials, and fittings.
Fluid Properties
Friction Head Loss
0.7520m
7.36kPa
Flow Properties
Velocity, flow rate, and Reynolds number for your pipe
1.019
Velocity (m/s)
2.000
Flow Rate (L/s)
50,736.44
Re — Turbulent
Darcy Friction Factor
Solved via the Colebrook-White equation
0.023694
Turbulent flow — Re = 50,736.44
Head Loss vs Pipe Length
Friction head loss and pressure drop along the pipe
Pressure Drop in All Units
Result converted to all supported pressure units
Step-by-Step Solution
Calculation walkthrough with your values
How the Friction Loss Calculator Works
Three proven methods for pipe friction loss calculation
Friction loss (also called head loss) is the energy lost when fluid flows through a pipe due to the pipe walls resisting flow. It depends on pipe diameter, length, material roughness, flow rate, and fluid properties. This calculator supports three industry-standard methods.
Darcy-Weisbach
hf = f × (L/D) × (v²/2g)
Any fluid • Most accurate
Hazen-Williams
hf = 10.67 × Q1.852 / (C1.852 × D4.87) × L
Water only • Simplest
Manning's Equation
hf = (10.29 × n² × Q²) / D5.333 × L
Gravity flow • Open channel
Example — 50mm steel pipe, 30m, 2 L/s water
Diameter
50mm
= 0.05 m
inner dia
Velocity
1.02
Q/A
m/s
Reynolds
50,736
Turbulent
Re
Head Loss
0.75
Darcy-Weisbach
meters
What Is Friction Loss?
Understanding energy loss in pipe systems
Friction loss (or friction head loss) is the loss of pressure or "head" that occurs when fluid flows through a pipe. It is caused by the viscous shear between the fluid and the pipe wall. The energy is converted to heat and is irrecoverable.
In practical systems, friction loss determines the pump size needed, the required pipe diameter, and the overall system efficiency. Fire protection systems use friction loss to ensure adequate nozzle pressure at the end of hose runs. Irrigation engineers size pipes to keep friction losses within acceptable limits.
Friction loss is measured in meters (or feet) of "head" — the height of a column of fluid that would exert the same pressure. To get pressure in kPa or psi, multiply by ρg (fluid density × gravitational acceleration).
Darcy-Weisbach vs Hazen-Williams: When to Use Each
Choosing the right calculation method
| Property | Darcy-Weisbach | Hazen-Williams | Manning |
|---|---|---|---|
| Fluid type | Any fluid | Water only | Water (gravity) |
| Flow regime | Laminar & turbulent | Turbulent only | Turbulent only |
| Key parameter | Surface roughness (ε) | C factor (empirical) | n coefficient |
| Accuracy | Highest (physics-based) | Good for water | Good for open channels |
| Complexity | Iterative (Colebrook-White) | Direct formula | Direct formula |
| Best for | Oil, gas, viscous fluids, precise engineering | Plumbing, fire protection, water supply | Sewers, drainage, gravity pipelines |
Pipe Materials Reference
Roughness, Hazen-Williams C factor, and Manning's n for common pipe materials
| Material | Roughness (mm) | H-W C | Manning n |
|---|---|---|---|
| Steel (new) | 0.045 | 140 | 0.011 |
| Steel (corroded) | 0.3 | 100 | 0.015 |
| Stainless Steel | 0.015 | 140 | 0.010 |
| Copper | 0.0015 | 140 | 0.011 |
| PVC | 0.0015 | 150 | 0.009 |
| HDPE | 0.007 | 150 | 0.009 |
| Cast Iron (new) | 0.25 | 130 | 0.012 |
| Cast Iron (corroded) | 1.0 | 100 | 0.015 |
| Galvanized Steel | 0.15 | 120 | 0.013 |
| Concrete | 0.3 | 120 | 0.013 |
Common Mistakes When Calculating Friction Loss
Errors that lead to incorrect pipe sizing
Using nominal instead of inner diameter
A “2-inch” pipe has an inner diameter of about 52.5 mm, not 50.8 mm. Using nominal size instead of actual inner diameter leads to significant errors because area scales with d².
Ignoring pipe fittings
Elbows, tees, and valves add significant equivalent length. A single globe valve adds the equivalent of 340 pipe diameters. Ignoring fittings can undersize pumps by 20–40% in typical systems.
Using Hazen-Williams for non-water fluids
Hazen-Williams is empirically calibrated for water only. Using it for oil, glycol, or other viscous fluids gives wildly incorrect results. Use Darcy-Weisbach for non-water applications.
Not accounting for pipe age
Pipe roughness increases dramatically with age due to corrosion, scaling, and biofilm. New steel has ε ≈ 0.045 mm; corroded steel can be 0.3–1.0 mm. Design for end-of-life conditions, not new pipe values.
Frequently Asked Questions
Common questions and detailed answers
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Last updated Apr 22, 2026