Darcy-Weisbach Head Loss Calculator
Enter the Darcy friction factor, pipe length, diameter and flow velocity. The calculator returns the friction head loss, and the pressure drop when you add the fluid density.
How to calculate Darcy-Weisbach head loss
- Enter the Darcy friction factor from a Moody chart or correlation.
- Enter the pipe length, inside diameter and flow velocity.
- Optionally add the fluid density to also get the pressure drop.
- Read the head loss in metres and the pressure drop in pascals.
Examples
Head loss in a 100 m pipe
f = 0.02, L = 100 m, D = 0.1 m, v = 3 m/s
head loss = 9.177 m
With water density
same pipe, density = 1000 kg/m3
pressure drop = 90000 Pa
Frequently asked questions
What is the Darcy-Weisbach equation?
Head loss equals f times length over diameter times velocity squared over 2 g. The pressure drop is density times g times that head loss.
Where do I get the friction factor?
Read it from a Moody chart, or compute it from the Colebrook or Swamee-Jain equation using the Reynolds number and relative roughness.
What is the difference between head loss and pressure drop?
Head loss is energy loss expressed as a height of fluid in metres. Multiplying by density and g converts it to a pressure drop in pascals.
Why does head loss grow with velocity squared?
Friction loss scales with the kinetic energy of the flow, which is proportional to velocity squared, so doubling velocity quadruples the loss.
Do I have to enter density?
No. Density is optional. Without it you still get the head loss in metres, and the pressure drop is reported as not available.
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