Pipe Sizing Calculator
Compressed air main diameter by pressure drop and air velocity
m³/min, compressor free air delivery (FAD)
bar, gauge
metres, from the compressor to the farthest consumer
Standard assumptions: fittings and valves +30%, allowable drop 7% of working pressure.
then press “Calculate”.
We help with system design and installation.
Consultation:
Why pipe diameter is the compressor’s “invisible” cost
Compressed air loses pressure to friction in the pipe. The narrower the pipe and the longer the line, the bigger the drop: it depends on the fifth power of the diameter, so halving the diameter raises the drop roughly 32 times. The compressor makes up the lost pressure with extra work: every additional bar means about 7% more electricity, and on a 24-hour line that often exceeds the price of the pipe itself within a year.
How the calculator works
Enter the compressor’s flow (m³/min), working pressure (bar) and line length (metres). The calculator adds +30% automatically for fittings and elbows and picks the smallest standard diameter at which the pressure drop stays within 7% and the air velocity stays within the allowed band (6–10 m/s on the main, up to 15 m/s on short connections). The result is economical but inside engineering norms.
Aluminium or plastic water pipe?
PP-R water pipe has a thick wall: at nominal Ø32 the bore is only 21 mm, against 28 mm for aluminium Ø32. Iron welding leaves an internal bead at every joint which, when over-melted, narrows the passage sharply, and each joint becomes a separate local resistance. So the same task needs a pipe two sizes larger in plastic, while resistance to oil, temperature and UV stays with aluminium. The calculator sizes both options so you can compare with numbers.
Frequently asked questions
Isn’t a 7% pressure drop a lot?
No. In industrial networks the total drop from the compressor to the last consumer is usually limited to 5–10%; at 7 bar, 7% is 0.49 bar. The calculator leans towards economy: it will not suggest an oversized pipe, but it will not cross that limit either. If sensitive pneumatics sit on the line, go one size up.
What if I have a ring main?
In a ring the air reaches every point from two sides, so each branch carries half the flow over half the distance. The calculator sizes an open line; we size ring mains separately for your project.
Which PP-R class is assumed?
PN20 (SDR 6), the most common thick-walled class. PN16 pipe has a slightly larger bore but less margin for air at 8–10 bar. For the final selection contact us: we will confirm the layout and diameters on your project.
