Engineering calculator reviewed for preliminary design use · Last updated: March 2026
Pipe pressure loss is calculated using the Darcy-Weisbach equation. Enter flow rate, fluid density and viscosity, pipe diameter, length, and roughness to find friction head loss. Use for pump sizing, piping design, and system evaluation.
What this calculator is used for
Pressure loss due to friction is one of the most fundamental calculations in
process and piping engineering. Any fluid flowing through a pipe loses energy
as heat because of wall friction, turbulence, and surface roughness.
Accurately estimating this pressure loss is essential for pump sizing, pipe
diameter selection, and overall system energy optimization.
Typical engineering use cases
Preliminary piping design during FEED or basic engineering
Estimating required pump head and motor power
Evaluating the impact of pipe diameter changes on energy consumption
Checking pressure margins for existing piping systems
Governing equation and methodology
This calculator is based on the Darcy–Weisbach equation, which is applicable
to both laminar and turbulent single-phase flow:
ΔP = f · (L / D) · (ρv² / 2)
The friction factor f is determined from the Reynolds number and pipe
roughness using standard correlations such as the Colebrook equation.
This approach is widely accepted in international engineering practice.
Engineering assumptions and limitations
Single-phase, steady-state flow
Fully developed flow inside the pipe
No phase change or chemical reaction
Minor losses (valves, elbows) should be added separately if required
Practical design notes
In real projects, calculated pressure loss should not be used as an absolute
value. Engineers typically apply design margins to account for fouling,
aging, and uncertainties in fluid properties. Pressure loss should also be
reviewed together with allowable velocity limits and erosion considerations.
It uses the Darcy-Weisbach equation: ΔP = f × (L/D) × (ρv²/2). The friction factor f is determined from the Moody chart correlation based on Reynolds number and relative roughness.
Does this include minor losses from fittings?
No. This calculator estimates straight-pipe friction loss only. For valves, elbows, and tees, use the Pipe Fittings Pressure Loss Calculator separately and add the results.
Can I use this for gas or two-phase flow?
This calculator assumes single-phase incompressible flow. For compressible gas at high Mach numbers or two-phase (gas-liquid) flow, different correlations are required.
These results are preliminary estimates for screening-level design use. They do not replace detailed engineering, code compliance verification, or vendor-certified calculations.