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Mechanical EngineeringP0

Darcy-Weisbach Pressure Drop Calculator

Calculate pressure drop in pipes using the Darcy-Weisbach equation with full parameter control.

Inputs
Enter your values below

0.015-0.03 typical for turbulent flow

Water = 1000, Air = 1.2

Result
Pressure Drop
—
Enter values and click Calculate
Formula
friction × length ÷ diameter × density × velocity² ÷ 2 ÷ 1000
Result unit: kPa

ΔP = f × (L/D) × (ρv²/2). Friction factor f (dimensionless), L/D in m, ρ in kg/m³, v in m/s; /1000 for kPa.

Introduction

The Darcy-Weisbach equation is the most accurate method for calculating pressure drop in pipes for all flow regimes. Requires an estimated Darcy friction factor (Moody chart or Colebrook equation).

Calculation Example

100m of 100mm pipe, f=0.02, water at 2m/s: ΔP = 40 kPa.

Inputs: friction=0.02, length=100, diameter=100, density=1000, velocity=2
Result: 40 kPa

Engineering Applications

  • •Pipeline design
  • •Pump head calculation
  • •HVAC hydronic design
  • •Process piping

Frequently Asked Questions

How do I find the friction factor?

Use the Moody chart or solve the Colebrook-White equation. For fully turbulent flow in commercial steel pipe, f ≈ 0.015-0.022.

When should I use Darcy-Weisbach vs Hazen-Williams?

Darcy-Weisbach works for all fluids and flow regimes. Hazen-Williams is only for water at typical temperatures and is simpler but less accurate.

Related Calculators

Pressure Drop Calculator (Darcy-Weisbach)Friction Loss CalculatorReynolds Number Calculator

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Disclaimer: Calculations are for reference and educational purposes only. Always verify results independently for engineering design. See full disclaimer.