Hydraulic calculator
Pipe Flow & Friction Loss Calculator
Calculate water velocity and straight-pipe friction loss from flow rate in US GPM. Supports Schedule 40 PVC, Schedule 80 PVC, and Type L copper using Hazen–Williams or Darcy–Weisbach for 100 ft of pipe.
Inputs
Results update automatically as you change any input.
Results
Calculation basis
Darcy–Weisbach: 100 ft of straight pipe. Water viscosity and density are calculated from the selected temperature. Turbulent friction factor is solved with the Colebrook equation using a smooth-pipe roughness of 0.000005 ft; laminar flow uses 64/Re.
Hazen–Williams mode uses the U.S. customary head-loss form hf = 0.002083L(100/C)1.85Q1.85/d4.8655, with head loss in feet, Q in US GPM, d in inches, and L in feet. Default C values are 150 for PVC and 140 for copper and can be edited.
TDH shown here is pipe friction only. It does not include fittings, valves, strainers, heaters, filters, equipment losses, elevation/static head, entrances, exits, or other minor losses.
About the Pipe Flow Calculator
This calculator estimates water velocity in feet per second and straight-pipe friction loss in feet of total dynamic head (TDH) per 100 feet of pipe. Enter a flow rate in US GPM and choose the nominal pipe size and material to compare hydraulic performance.
Available materials include Schedule 40 PVC, Schedule 80 PVC, and Type L copper. Friction loss can be calculated with the Hazen–Williams method or the Darcy–Weisbach method. Darcy–Weisbach uses the selected water temperature when determining water properties.
Use the result as a straight-pipe friction estimate. A complete system TDH calculation should also account for fittings, valves, equipment, elevation changes, entrances, exits, and other system losses.