Where does friction factor f come from?

f must come from a Moody diagram, Colebrook-White iteration, or another explicit model for your Re and relative roughness. This tool does not infer f from roughness automatically.

Does this include fittings and valves?

Only if you fold equivalent length into L or treat minor losses separately. The core equation models straight-pipe friction with the f you supply.

Is compressible flow included?

No. The implementation assumes incompressible fluid with uniform density along the segment for this estimate.

Pressure Drop Calculator

This calculator applies the Darcy–Weisbach relation for incompressible flow in a circular pipe: mean velocity from continuity and pressure drop from friction factor, length-to-diameter ratio, density, and velocity head. It is intended for quick checks and learning, not stamped hydraulic design.

Free · No limits · Runs in your browser

How to use

1Enter volumetric flow rate and inside pipe diameter (use consistent real inside diameter, not nominal schedule guess without verification).
2Enter developed pipe length along the flow path for straight-run loss with your chosen friction factor.
3Set fluid density (defaults near liquid water) and the Darcy friction factor f for your line Reynolds number and roughness model.
4Read mean velocity and pressure drop; switch output units as needed.

Frequently asked questions

Where does friction factor f come from?: f must come from a Moody diagram, Colebrook-White iteration, or another explicit model for your Re and relative roughness. This tool does not infer f from roughness automatically.
Does this include fittings and valves?: Only if you fold equivalent length into L or treat minor losses separately. The core equation models straight-pipe friction with the f you supply.
Is compressible flow included?: No. The implementation assumes incompressible fluid with uniform density along the segment for this estimate.