Enter flow once
The tool converts the flow units automatically and uses the SI value in the selected pressure-drop calculation.
Engineering Workbench · Flow & Pressure Drop
Flow Rate & Pressure Drop Calculator
Convert volumetric flow, calculate velocity and estimate pressure drop for a round pipe, a screen with a known loss coefficient, or a porous filter medium.
Important: choose the model that matches the physical system. A pipe friction equation, screen loss coefficient and porous-media permeability are not interchangeable.
Enter operating conditions
Shared flow and fluid data are used by the selected model.
Water near 20°C ≈ 998 kg/m³; air near 20°C ≈ 1.204 kg/m³.
1 cP = 1 mPa·s = 0.001 Pa·s.
6m³/h
100L/min
26.417US gpm
3.531cfm
Pressure-drop model
Example reference: commercial steel ≈ 0.045 mm. Use project-specific data.
Obtain K from test data, supplier data or a validated correlation.
Use measured permeability for the actual medium and compression state.
Engineering results
Darcy–Weisbach estimate for straight round pipe.
Pipe velocity0.849 m/s2.785 ft/s
Reynolds number42,272turbulent
Pressure drop1.760 kPa1,760 Pa
Other pressure units0.01760 bar0.2553 psi
Darcy friction factor0.02448Straight-pipe friction only; fittings are excluded.
Formula used
ΔP = f × (L/D) × ρv²/2One workflow, three different models
| Model | Pressure-drop equation | Required engineering input | Do not use for |
|---|---|---|---|
| Round pipe | Darcy–Weisbach | ID, length, roughness, density, viscosity | Filter-media resistance |
| Screen / local loss | ΔP = Kρv²/2 | Effective area and validated K | Unknown screen geometry without K |
| Porous medium | Darcy Law: ΔP = μLv/k | Area, thickness, permeability, viscosity | High-speed inertial flow or clogged media |
How to use the workbench
Select the physical model
Choose pipe, screen/K or porous media according to how resistance is defined for the real component.
Validate the input data
Use measured viscosity, roughness, loss coefficient or permeability whenever the result affects equipment selection.
Important calculation boundaries
The pipe model uses laminar f = 64/Re and a Swamee–Jain turbulent approximation. The transition region is inherently uncertain, and fittings, valves, entrances and elevation are excluded.
The screen model does not invent a universal K value. Wire diameter, open area, weave, thickness, layer count and Reynolds number all affect K.
The porous model is the viscous Darcy term only. At higher velocities, an inertial Forchheimer term may be required. Fouling and compression can also change permeability.
For gases, density and viscosity must match the actual calculation condition. A standard flow value must first be converted to actual volumetric flow.
Frequently asked questions
Can one pressure-drop formula be used for pipes and filters?
No. Pipe wall friction, screen local loss and porous-media resistance use different physical models and input data.
Where do I get the screen loss coefficient K?
Use supplier data, laboratory test results or a validated correlation for the actual weave, open area, thickness and Reynolds-number range.
What permeability should I enter?
Use permeability measured for the actual medium, manufacturing lot and compression state. Nominal pore size is not a permeability value.
Does the pipe result include elbows and valves?
No. Add minor losses separately using their K values or equivalent lengths.
Can this predict a dirty filter pressure drop?
No. Fouling changes resistance over time. Dirty-element pressure drop requires loading data, test curves or a validated fouling model.
Why must gas standard flow be corrected?
Pressure drop depends on actual velocity and density. Standard and actual volumetric flow differ when temperature or absolute pressure changes.
Need a validated filter pressure-drop calculation?
Share the fluid, flow basis, temperature, pressure, medium, effective area and test data with our engineers.
Engineering disclaimer: Results are preliminary estimates based on the selected model and user-supplied inputs. They do not replace test data, system calculations or qualified engineering review.
