Compressed Air Pipe Sizing and Pressure Drop Calculator
- Sullair dealer since 1984
- Serving industry since 1978
- No form fill, nothing gated
What this calculator tells you
Check whether your air line is sized right. Undersized pipe forces higher discharge pressure, and that costs energy every hour you run.
Your Pipe Run
Results
Pressure drop across the run:
0 PSI
How this is calculated
- Pressure drop (PSI) = 0.1025 x L x Q^1.85 / (d^5 x (P + 14.7))
- L = pipe length in feet including the equivalent length of elbows, tees, and valves. Q = flow in SCFM. d = inner diameter in inches. P = gauge pressure in PSI.
- Verdict: under 3 PSI is good, 3 to 5 PSI is marginal, over 5 PSI is undersized.
- Excess-drop cost: each 2 PSI of extra pressure is about 1% of compressor energy. Annual energy assumed = 50 HP x 0.746 / 0.93 motor efficiency x 4,160 hours x $0.12/kWh.
Estimates only. Actual results depend on your equipment and operating conditions. Call 800.825.3222 for exact sizing.
Common questions
How much pressure drop is acceptable in compressed air piping?
A well designed compressed air system loses less than 3 PSI between the compressor and the farthest point of use. A drop of 3 to 5 PSI is marginal, and anything over 5 PSI means the piping is undersized, forcing you to run higher discharge pressure and waste energy. Every 2 PSI of extra pressure costs about 1 percent of compressor energy.
How do I calculate pressure drop in a compressed air pipe?
A common empirical formula is pressure drop = 0.1025 x L x Q^1.85 / (d^5 x (P + 14.7)), where L is pipe length in feet including the equivalent length of fittings, Q is flow in SCFM, d is inner diameter in inches, and P is gauge pressure in PSI. Because diameter is raised to the fifth power, one pipe size up cuts the drop dramatically.
What size pipe do I need for 100 CFM of compressed air?
It depends on run length and pressure. At 100 PSI over a 200 foot run including fittings, 100 SCFM needs roughly a 3 to 4 inch line to stay under a 3 PSI drop by the standard empirical formula. Short runs can go smaller. Always include the equivalent length of elbows, tees, and valves, which often doubles the effective length.
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These are estimates. An air audit gives you measurements.
A week of logged data on your actual system beats any rule of thumb. Our engineers run no-obligation compressed air audits across 14 Midwest locations.