Pipe Pressure Drop Calculator
Estimate liquid pipeline pressure drop from flow rate, internal diameter, pipe length, roughness, density, viscosity, fittings and elevation.
How to use this calculator
- 1
Enter flow rate and pipe internal diameter.
- 2
Enter straight length, roughness, density and viscosity.
- 3
Add the combined fittings K factor and elevation difference.
- 4
Select the pressure unit and calculate the estimated total pressure change.
Pipe pressure drop affects pump selection, flow stability, control-valve authority and available pressure at instruments or equipment. The Darcy–Weisbach method relates friction loss to pipe geometry, velocity, fluid density and friction factor.
This calculator also includes a combined fittings K factor and static elevation term. It is intended for incompressible single-phase liquids; gas, steam, flashing, two-phase and highly non-Newtonian services require a more appropriate method.
Formula and assumptions
Darcy friction factor is 64/Re for laminar flow and uses the Swamee–Jain approximation for turbulent flow. Transitional flow remains uncertain.
Examples and guidance
- Positive elevation means the outlet is above the inlet and adds static pressure requirement.
- Enter the combined K values for valves, bends, tees, entrances and other fittings.
Continue your calculation
Move between related pressure, level, flow, signal and measurement calculations without starting a new search.
Questions and answers
Does the calculator support gases or steam?
No. It assumes incompressible, single-phase liquid flow with constant density and viscosity.
What is the fittings K factor?
K is the sum of dimensionless minor-loss coefficients for valves, bends, tees, entrances, exits and other components in the flow path.
What happens in the transitional Reynolds-number range?
Flow between approximately Re 2300 and 4000 is unstable. The displayed result is only an estimate and should not be used as a final design value.