Calculator inputs
Example data table
This worked example uses a 120 m commercial steel pipe carrying water at 20°C with minor losses and a 6 m elevation rise.
| Length | Diameter | Flow | Roughness | Reynolds | f | Total K | Velocity | Friction drop | Total head |
|---|---|---|---|---|---|---|---|---|---|
| 120 m | 100 mm | 18 L/s | 0.045 mm | 228,379 | 0.01844 | 6.50 | 2.292 m/s | 75.051 kPa | 13.667 m |
Formula used
The calculator uses Darcy–Weisbach for major loss and standard minor-loss coefficients for fittings.
V = Q / A, where A = πD² / 4
Re = ρVD / μ
f = 64 / Re for laminar flow.
f = 0.25 / [log10(ε / 3.7D + 5.74 / Re^0.9)]² for transitional and turbulent flow.
h_major = f(L / D)(V² / 2g)
h_minor = K(V² / 2g)
ΔP_friction = ρgh_friction
ΔP_total = ρg(h_friction + Δz)
P_pump = ρgQH / η, using positive total head and entered efficiency.
How to use this calculator
- Enter the straight pipe length and inside diameter.
- Select a material preset or provide custom roughness.
- Set the flow rate in your preferred unit.
- Choose water with temperature, or enter custom fluid properties.
- Add elevation change and fitting counts to capture minor losses.
- Enter pump efficiency for a basic power estimate.
- Press the calculate button to show results above the form.
- Use the graph, table, and exports for reporting or checks.
Frequently asked questions
1) What does this calculator estimate?
It estimates friction pressure loss, head loss, Reynolds number, friction factor, total pressure change, and approximate pump power for liquid flow in a pipe system.
2) Does elevation change affect the friction result?
No. Friction pressure drop only covers wall friction and fittings. Elevation is added separately to show the total pressure change between inlet and outlet.
3) Why are minor losses important?
Elbows, valves, entrances, exits, meters, and tees can add meaningful resistance. In short runs, fitting losses may rival or exceed straight-pipe friction losses.
4) Which friction-factor method is used?
Laminar flow uses 64/Re. Transitional and turbulent flow use the Swamee–Jain explicit relation, which is a practical approximation to the Colebrook equation.
5) Can I use fluids other than water?
Yes. Switch to the custom fluid mode and enter density and dynamic viscosity. The calculator then uses those properties for Reynolds number, head loss, and pressure drop.
6) What roughness value should I choose?
Start with the material preset. For aged, scaled, or lined systems, replace the preset with a project-specific roughness value from design standards or measured data.
7) Why does pressure loss rise quickly with flow?
Velocity increases with flow rate, and both major and minor losses depend on the velocity head term V²/2g. That makes pressure loss grow rapidly.
8) Is the pump power result exact?
No. It is a preliminary estimate based on entered efficiency and total head. Real pump selection also considers pump curves, motor losses, NPSH, control margin, and operating range.