Pipe Pressure Drop Calculator

Calculate pressure drop, head loss, and Reynolds number for pipe flow using the Darcy-Weisbach equation.

Inputs

Pipe Length

Pipe Inner Diameter

Flow Velocity

m/s

Fluid Density

kg/m³

Darcy Friction Factor

Total Fittings K-Factor

Tab to move between fields

Results

Total Pressure Drop

90,000 Pa

Head Loss

9.17 m

≈ 5 adult heights

Reynolds Number100,000

Flow Regime2 (1=laminar, 2=turbulent)

How to Use This Calculator

Enter the Pipe Length in meters and the Pipe Inner Diameter in mm.
Enter the Flow Velocity in m/s — typical process piping velocities are 1–3 m/s for liquids and 10–30 m/s for gases.
Enter the Fluid Density in kg/m³: water ≈ 1000, air at ambient ≈ 1.2, typical process oils ≈ 850.
Enter the Darcy Friction Factor — for fully turbulent flow use the Moody chart or Colebrook equation; turbulent flow values typically range from 0.01–0.05.
Enter the Total Fittings K-Factor — sum the K values for all valves, elbows, tees, and reducers from the K-method tables.
Read the Total Pressure Drop in Pa and Head Loss in m, and confirm the Reynolds Number to verify the assumed flow regime.

How the result changes with Flow Velocity

Flow Velocity	Total Pressure Drop	Head Loss
5.01	564,752.25 Pa	57.57 m
18	7,290,000 Pa	743.12 m
33	24,502,500 Pa	2,497.71 m
45	45,562,500 Pa	4,644.5 m

What each input means

Pipe Length: Total straight length of the pipe in meters.
Pipe Inner Diameter: Internal diameter of the pipe in millimeters.
Flow Velocity: Average fluid velocity in the pipe.
Fluid Density: Density of the fluid. Water is approximately 1000 kg/m³.
Darcy Friction Factor: Darcy-Weisbach friction factor. Typical values: 0.01-0.05 for turbulent flow.
Total Fittings K-Factor: Sum of resistance coefficients for all fittings, valves, and bends.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Pipe Length = 100, Pipe Inner Diameter = 50, Flow Velocity = 2, Fluid Density = 1000 = 6 input(s) provided
Calculate Total Pressure Drop
Total Pressure Drop
90000 = 90000
Calculate Head Loss
Head Loss
9.174 = 9.174
Calculate Reynolds Number
Reynolds Number
100000 = 100000
Calculate Flow Regime
Flow Regime
2 = 2

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