Pipe Velocity Calculator

Calculate liquid velocity from flow rate and pipe inside diameter.

Calculator

Velocity (v) —
Flow area (A) —

Formula

Liquid velocity in the pipe is calculated as:

v = Q / A
A = π · D² / 4

Where:

  • v = liquid velocity [m/s]
  • Q = flow rate [m³/s]
  • A = pipe flow area [m²]
  • D = pipe inside diameter [m]

Engineering note

Pipe velocity limits are usually defined by project/company standards rather than by one universal API or ISO value. As a practical preliminary check for clean water-like liquids:

  • Pump suction line: typically about 0.6–1.5 m/s, often kept below 2 m/s to limit suction losses and protect NPSHa.
  • Pump discharge line: typically about 1.5–3.0 m/s, sometimes higher if pressure drop, noise and erosion are acceptable.
  • Viscous, dirty, erosive or flashing liquids: use more conservative limits and verify against the project specification.

For final design, check the applicable project standard, client specification, material limits, erosion/corrosion risk, allowable pressure drop and NPSH margin.