Pipe Sizing

How to use this calculator

Select a pipe diameter for a given flow, length and allowable pressure drop.

1. Enter design flow in CFM and system pressure.
2. Enter the equivalent length of run including fittings and valves.
3. Enter the allowable pressure drop for that run.
4. Read the minimum diameter and step up one size if future expansion is likely.

Frequently asked questions

What size air line do I need for 100 CFM?

For a 100 ft run at 100 psig with about 2 psi of drop, 1-1/4 in pipe is a typical choice; longer runs or higher flow move you to 1-1/2 in or 2 in.

How do fittings affect pipe sizing?

Elbows, tees and valves add equivalent length. A 90° elbow on 1 in pipe adds roughly 2.5 ft, and a globe valve can add 30 ft or more.

Is a loop better than a branch layout?

Yes. A loop feeds each drop from two directions, roughly halving effective length and pressure drop, and it makes future taps easier.