Hydraulics

Pipe flow calculator

Estimate the volumetric flow in a pipe from the internal diameter and average fluid velocity. The result is useful for water circuits, basic sizing checks, and quick planning.

Calculate flow View worked example

Outputs

Liters per minute
Cubic meters per hour
Pipe area

Worked example

What flow does a 20 mm pipe carry at 1.5 m/s?

Example build-up

Internal diameter: 20 mm. Average velocity: 1.5 m/s.

Estimated flow = 28.3 L/min, which is 1.70 m3/h.

Formula

Flow = area × velocity

Area = pi × (diameter / 2)^2

Calculator

Enter the pipe details

Internal diameter (mm) Average velocity (m/s)

Measurement note

This is a straight volumetric estimate. Real systems are affected by friction, fittings, pumps, and pressure loss.

Flow rate

0.0 L/min

Flow rate

0.00 m3/h

Pipe area

0.0000 m2

How to use it

What the inputs mean

Diameter

Use the internal pipe diameter, not the outside diameter, for the flow estimate.

Velocity

Higher velocity means more flow, but also more friction and noise in real installations.

Use case

Good for quick water-flow planning, rough sizing, and comparing pipe sizes.

Pipe flow guide

Read the guide before choosing a pipe size.

Open guide

How much water through a 15 mm pipe?

See a fast example for a small pipe.

Open page

How much water through a 22 mm pipe?

Compare a mid-size domestic pipe.