Physics

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Friction Loss Calculator.

Calculate Darcy–Weisbach head and pressure loss with every pipe and fluid variable entered explicitly.

On-device calculationNo signup
01

Set your values

Results update as you type.

Head loss: 0.40788649 m

Head loss

0.00000000m
Pressure loss: 4,000 Pa

Pressure loss

0.00000000Pa

Results update automatically as you type.

This is a Darcy–Weisbach calculation using your friction factor. It does not select a pipe code, pump, material limit, or design margin.

Use Cases

Designing piping systems

Engineers use this calculator to estimate friction losses in water or other fluid pipelines, helping to select pump sizes and pipe diameters.

Example: Estimate head loss for a 100 m pipe with 0.2 m diameter carrying water at 2 m/s.

Educational demonstrations

Students and educators can quickly compute friction losses for various flow conditions to understand fluid mechanics principles.

Example: Compare head loss for different flow velocities or pipe lengths.

Frequently Asked Questions

What does the Darcy–Weisbach equation calculate?
It calculates the head loss (in meters) due to friction as fluid flows through a pipe. The calculator also converts this head loss to pressure loss using the fluid density and gravity.
What units should I use for the inputs?
Use SI units: pipe length and diameter in meters, fluid density in kg/m³, flow velocity in m/s, and gravity in m/s². The Darcy friction factor is dimensionless.
How is pressure loss derived from head loss?
Pressure loss is calculated as the product of fluid density, gravity, and head loss (ΔP = ρ × g × h_f). The calculator uses the gravity value you input.

Tips & Common Mistakes

Tips

  • Ensure the Darcy friction factor is appropriate for your flow regime (laminar or turbulent) and pipe roughness.
  • Use consistent SI units for all inputs to get accurate results in meters and pascals.
  • Double-check the flow velocity: it should be the average velocity in the pipe, not the volumetric flow rate.
  • Remember that gravity is typically 9.81 m/s² on Earth, but you can adjust it for other conditions.

Common Mistakes to Avoid

  • Using diameter in centimeters or millimeters instead of meters, leading to incorrect head loss.
  • Confusing the Darcy friction factor with the Fanning friction factor (which is 4 times smaller).
  • Forgetting to convert pressure loss to desired units (e.g., kPa or bar) after calculation.

Last updated: August 13, 2026