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Calculation Machine

Compressed Air Pipe Size Calculator

Pipe diameter for a compressed air line.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Pressure drop
346.47 psi
Verdict
Too much — increase pipe size
Minimum diameter for 2 psi
2.1 in
Suggested nominal size
1-1/2" or larger
Velocity guide
Keep under 20 ft/s in mains

Quick answer

Compressed air lines are sized so total pressure drop stays under about 2 psi from compressor to tool.

The formula

drop rises with length and falls with the fifth power of diameter

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Flow40 SCFM
  • Line pressure100 psi
  • Pipe length100 ft
  • Pipe inside diameter0.75 in

Result

  • Pressure drop346.47 psi
  • VerdictToo much — increase pipe size
  • Minimum diameter for 2 psi2.1 in
  • Suggested nominal size1-1/2" or larger
  • Velocity guideKeep under 20 ft/s in mains

How to use the Compressed Air Pipe Size Calculator

  1. 1Enter the flow the line must carry and the operating pressure.
  2. 2Include the full run length plus equivalent length for fittings.
  3. 3Increase diameter until pressure drop is under 2 psi.

Frequently asked questions

Does 1 psi matter?

Every 2 psi of drop costs about 1% in compressor energy, and tools lose torque quickly below rating.

Loop or dead-end?

A ring main halves the effective length and evens out pressure at every drop.

About this calculator