Pressure Drop Calculator
Pressure Drop Calculator: Darcy-Weisbach Friction Loss in Ducts and Pipes
As gas travels through a duct or pipe, friction against the walls steadily consumes pressure. The Darcy-Weisbach equation is the standard way engineers quantify this loss, and this calculator applies it directly using pipe geometry, gas properties, and velocity.
The Formula
dP = f × (L/D) × (ρ × V² / 2)
Worked Example
Gas at 1.2 kg/m3 flows at 15 m/s through a 50 m length of 0.3 m diameter duct with a friction factor of 0.02.
dP = 0.02 × (50/0.3) × (1.2 × 15² / 2) = 450 Pa
How to Use This Calculator
- Enter the Darcy friction factor for the pipe (depends on roughness and Reynolds number).
- Enter the pipe length and diameter in meters.
- Enter the gas density and average velocity.
- Click Calculate to get the pressure drop in Pascals.
Related Calculations
Check flow regime first with the Reynolds Number Calculator to select an appropriate friction factor.