Calculator Inputs
Use the form below to model friction, fitting, and elevation effects in one place.
Formula Used
The calculator uses the Darcy–Weisbach framework for major losses, combines minor losses with a total fitting coefficient, and adds static pressure from elevation change.
Velocity: v = Q / A
Reynolds number: Re = ρvD / μ
Major loss: ΔPmajor = f (L/D) (ρv²/2)
Minor loss: ΔPminor = K (ρv²/2)
Static change: ΔPstatic = ρgΔz
Total change: ΔPtotal = ΔPmajor + ΔPminor + ΔPstatic
Laminar flow uses f = 64/Re. Transitional flow is smoothly interpolated. Turbulent flow uses the Swamee–Jain explicit relation with relative roughness.
How to Use This Calculator
- Select metric or imperial units first.
- Choose a fluid preset or enter custom density and viscosity.
- Choose a material preset or enter custom roughness.
- Enter pipe length, diameter, and flow rate.
- Add elevation change and total minor loss coefficient.
- Submit the form to calculate the pressure change.
- Review pressure components, head losses, Reynolds number, and regime.
- Use the export buttons to save the result table.
Example Data Table
This sample illustrates a typical water system with commercial steel piping and moderate fitting losses.
| Parameter | Example Value | Unit |
|---|---|---|
| Pipe length | 120 | m |
| Inner diameter | 80 | mm |
| Flow rate | 18 | m³/h |
| Roughness | 0.045 | mm |
| Density | 998 | kg/m³ |
| Viscosity | 1.0 | cP |
| Elevation rise | 6 | m |
| Total K | 8.5 | — |
Frequently Asked Questions
1. What does this calculator estimate?
It estimates total pressure change through a pipe segment by combining friction losses, fitting losses, and elevation effects. It also reports head loss, Reynolds number, friction factor, and flow regime.
2. Which pressure loss method is used?
The calculator uses the Darcy–Weisbach equation for major loss. Minor losses are added with a total K value. Static pressure change is included from elevation rise or drop.
3. Why does elevation change affect the result?
Lifting fluid upward requires extra pressure, while downhill flow can recover pressure. That static component is separate from friction and fitting losses, so it must be shown clearly.
4. What is the minor loss coefficient, K?
K represents extra energy loss from valves, bends, tees, entrances, exits, reducers, and similar fittings. Sum the fitting coefficients for the full pipe section and enter the total.
5. Can I use imperial units?
Yes. Switch the unit system to imperial. The calculator converts your inputs internally to SI units, then returns pressure and head values in imperial-friendly outputs.
6. How is friction factor determined?
Laminar flow uses 64 divided by Reynolds number. Transitional flow is interpolated. Turbulent flow uses the Swamee–Jain relation, which includes both Reynolds number and relative roughness.
7. What roughness value should I enter?
Use the material preset when available. For aged or coated pipes, enter a custom value that better reflects field conditions. Roughness strongly affects turbulent pressure loss.
8. When should I export the results?
Export after reviewing the calculated table. CSV works well for spreadsheets and audits. PDF is useful for design notes, client attachments, and quick documentation.