CalcPanel

Pipe Pressure Drop Calculator

Estimate friction loss from flow, internal diameter, length, and roughness.

Pipe inputs

Visible default for the selected material. Edit it when the pipe is worn or lined.
Advanced settings
0 to 100 °C fills density and viscosity from a planning table. Leave blank to keep the 20 °C round defaults.

Fitting counts use K v² / (2 g). Default K values are planning assumptions, not a fitting catalog.

About this calculator

One task: velocity, Reynolds number, friction factor, and pressure drop for a single pipe. Static lift and shaft power stay on pump sizing. More plant tools are on the power calculators hub.

Result

Pressure drop 4.95 psi (34.16 kPa, 0.342 bar)

Velocity 1.56 m/s. Reynolds number 78,906. Friction factor 0.0188. Head loss 11.45 ft (3.49 m). About 4.58 ft and 1.98 psi per 100 ft of straight pipe.

Planning estimate. Confirm roughness, fittings, and fluid properties before you buy pipe or a pump.

Assumptions: water near 20°C, density 998 kg/m³, viscosity 0.001 Pa·s, and PVC roughness 0.0015 mm. Results are estimates based on the inputs and assumptions provided. Actual piping performance may vary with installation, fluid properties, and manufacturer data.

Continue Your Calculation

Need static lift and shaft power as well? Continue in pump sizing with this flow and pipe.

Pump sizing →

Default roughness and fitting K

InputDefaultMeaning
Water998 kg/m³, 0.001 Pa·sAbout 20°C when temperature is not entered
PVC / copper0.0015 mmSmooth thermoplastic or drawn tube
Steel / stainless / cast iron0.045 / 0.015 / 0.26 mmNew commercial pipe, planning values
Elbow / valve / tee / entrance / exitK = 0.9 / 0.2 / 0.6 / 0.5 / 1.0Planning assumptions you can edit

Formula

Flow sets velocity. Velocity and diameter set the Reynolds number. Reynolds number and roughness set the friction factor. Head loss is hf = f L v² / (2 g D), and pressure drop is ρ g hf.

Laminar flow (Re < 2300) uses f = 64 / Re. Turbulent flow uses the Haaland 1983 explicit approximation of Colebrook-White. Fitting loss, when you enter a count, is K v² / (2 g) and is added to the straight-pipe loss. This page does not calculate pump head. Continue with pump sizing for static lift and shaft power.

Worked example

50 GPM through 250 ft of 2 in PVC, roughness 0.0015 mm, water at about 20°C, no fittings.

The same engine used by pump sizing returns velocity 1.56 m/s, Reynolds number 78,906, friction factor 0.0188, head loss 11.45 ft (3.49 m), and pressure drop 4.95 psi (34.16 kPa, 0.342 bar). Straight-pipe loss is about 4.58 ft and 1.98 psi per 100 ft. A high-velocity or high-loss warning, when it appears, still leaves this result in place and points you at a larger diameter.

FAQ

What is pipe pressure drop?

It is the pressure lost to friction and fittings between two points in a straight pipe run. The page also shows the same loss as feet and meters of fluid head.

How do Reynolds number and friction factor affect the result?

Velocity and diameter set the Reynolds number. That number, with pipe roughness, sets the friction factor used in the Darcy-Weisbach head loss.

What should I do if I see a high velocity warning?

The warning does not stop the calculation. Increase the internal diameter or reduce the flow and calculate again. Very high velocity usually means a high friction loss.

Does this page include pump head?

No. Static lift, discharge pressure, and pump efficiency belong on the pump sizing calculator. This page only accounts for pipe and fitting loss.