Darcy-Weisbach Friction Loss Calculator

Calculate pressure drop in plumbing pipes using the Darcy-Weisbach equation, accurate for all flow regimes.

Water flow rate.
GPM
Internal diameter.
inches
Total pipe length.
feet
Absolute roughness: 0.000005 (copper/PEX), 0.00015 (steel), 0.0002 (cast iron).
feet

Results

Pressure Loss-PSI
Velocity-ft/s
Reynolds Number-
References: Based on Darcy-Weisbach equation per ASHRAE Fundamentals