Pipe Size Calculator
Estimates the pipe size for a flow rate.
Minimum inside diameter
— mm
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
In inches — in
Next common size — mm
Reading this —
The formula
d = √(4 × flow ÷ (π × velocity))
Flow equals area times velocity, so a target velocity fixes the area and therefore the diameter.
What to watch out for
Long runs and many fittings lose more pressure, which is not modelled here.
Frequently Asked Questions
What size pipe for 30 L/min?
About 20.6 mm inside at 1.5 m/s.