Darcy-Weisbach Pressure Loss Calculator

Calculate pipe velocity, Reynolds number, friction factor, head loss and pressure drop.

Total head loss
0.175 m
Pressure loss 1.71 kPa
Mean velocity 0.637 m/s
Reynolds number 63,662
Darcy friction factor 0.02157
Inputs
m³/s
Volumetric flow rate.
m
Pipe internal diameter, not nominal size.
m
Straight pipe length.
m
Absolute internal surface roughness.
m²/s
Fluid kinematic viscosity at operating temperature.
kg/m³
Fluid density.
dimensionless
Sum of fitting, entrance, exit, or valve loss coefficients.
Results & Graph
Total head loss
0.175 m
Pressure loss
1.71 kPa
Mean velocity
0.637 m/s
Reynolds number
63,662
Darcy friction factor
0.02157

Pipe head-loss contributors

Graph 1 • Entered design case Domain-specific illustration generated from the active calculator inputs.
PIPE FLOW AND ENERGY LOSSInletOutletv=0.637 m/s • pressure falls with length, roughness and fittings
Graph 2 • Engineering outputs Separates straight pipe friction from entered local losses.
Friction head 0.134 m Fitting head 0 m
Graph 3 • Calculated response Linear length scaling for unchanged flow and diameter.
0m 0.5m 1.1m 0 m: 0 m 0 0 m 10 m: 0.058 m 0.1 10 m 20 m: 0.117 m 0.1 20 m 30 m: 0.175 m 0.2 30 m 40 m: 0.233 m 0.2 40 m 50 m: 0.292 m 0.3 50 m 60 m: 0.35 m 0.4 60 m
Summary: Total estimated head loss is 0.175 m (1.71 kPa).
Summary: At 0.637 m/s, the estimated friction factor is 0.02157 (Re=63,662); straight pipe and entered minor losses produce 0.175 m head loss.
⚠️ Uses Swamee–Jain for turbulent flow and 64/Re for laminar flow; transitional flow near Re 2,300 is uncertain. Single-phase, incompressible, fully developed flow assumed.

Formula & Mathematical Methodology: Darcy-Weisbach Pressure Loss Calculator

hL=(fL/D+ΣK) v²/(2g)
Re=vD/ν
f=64/Re (laminar), Swamee–Jain approximation (turbulent)
hL=(fL/D+ΣK) v²/(2g); Re=vD/ν; f=64/Re (laminar), Swamee–Jain approximation (turbulent)
  • : Mean pipe velocity
  • : Reynolds number
  • : Darcy friction factor
  • : Combined minor-loss coefficient

Rounding: Displayed values are rounded for readability; calculations retain full floating-point precision.

Worked Example: 5 L/s through 100 mm pipe over 30 m

Estimate water flow losses with a 0.045 mm roughness and entered fittings coefficient.

  1. Compute pipe area and average velocity.
  2. Determine Reynolds number and friction factor.
  3. Combine straight-pipe and minor head losses.
Result: The result reports total head loss and corresponding pressure drop.

Frequently Asked Questions

What is the roughness value for my pipe?

Use a verified material/condition reference or manufacturer data; roughness changes with material, age, corrosion, and deposits.

Science & Engineering • Fluid Mechanics Guide

How to Use the Darcy-Weisbach Pressure Loss Calculator: Practical Guide & Visual Analysis

Enter SI flow, diameter, length, roughness, viscosity, density, and fitting loss coefficient. Whether you are researching darcy weisbach calculator, pipe pressure drop calculator, friction head loss calculator, reynolds number pipe calculator, this interactive tool helps you estimate straight-pipe Darcy–Weisbach friction and minor losses for steady, incompressible flow.

Interpreting the 3 Custom Visual Graphs & Key Outputs

As you adjust Flow Rate, Inside Diameter, Pipe Length, Absolute Roughness, the calculator immediately computes Primary result, Supporting calculation metrics, Three calculator-specific visualizations and updates all three domain-specific SVG charts in real time. Instead of relying on a single static figure, you can inspect the primary domain diagram, component breakdown, and multi-point trajectory curve to see how changing your inputs shifts the final result. Use the Compare (up to 3 scenarios) button to evaluate side-by-side variations before making a decision.

Real-World Benchmark & Planning Tips (Global; user-entered values, assumptions and currency)

In our benchmark scenario (5 L/s through 100 mm pipe over 30 m), The result reports total head loss and corresponding pressure drop. Keep in mind that steady, fully developed, single-phase incompressible flow. For related calculations in Science & Engineering, explore Pipe Volume, Pool & Tank Gallons, Water Flow Rate (GPM) & HVAC CFM Calculator, Pump Power and Operating Cost Calculator, Unit Conversion Calculator.