Compressed Air Pipe Sizing

Size piping for compressed air distribution systems

Calculation Type

Pipe Material

Air Flow Requirements

Air Flow (SCFM) Standard cubic feet per minute

Operating Pressure (PSIG)

Pipe Length (feet)

Max Pressure Drop (PSI) Recommended: 3% of system pressure

Sizing Results

Recommended Pipe Size --

Pressure Drop --

Air Velocity --

ACFM (Actual CFM) --

Compression Ratio --

Note: Keep velocity under 30 ft/s for mains, 50 ft/s for branches.

Pipe Capacity at 100 PSIG

Pipe Size	100 ft	200 ft	500 ft
1/2"	12 SCFM	8 SCFM	5 SCFM
3/4"	31 SCFM	22 SCFM	14 SCFM
1"	76 SCFM	54 SCFM	34 SCFM
1-1/4"	155 SCFM	110 SCFM	69 SCFM
1-1/2"	260 SCFM	184 SCFM	116 SCFM
2"	570 SCFM	403 SCFM	255 SCFM
3"	1600 SCFM	1130 SCFM	715 SCFM

Based on 3 PSI pressure drop, Schedule 40 steel pipe

Design Guidelines

Main lines: Max 30 ft/s velocity
Branch lines: Max 50 ft/s velocity
Pressure drop: Max 3% of system pressure
Receiver: 1 gallon per SCFM typical
Drip legs: Every 150-200 ft and low points
Slope: 1/8" per foot toward drains

Compressed Air Formulas

Pressure Drop (Darcy)

ΔP = (C x L x Q^1.85) / (CR x d⁵)

C = Material constant
L = Equivalent length (ft)
Q = Flow rate (SCFM)
CR = Compression ratio
d = Inside diameter (in)

Compression Ratio

CR = (P_gauge + 14.7) / 14.7

At 100 PSIG:
CR = (100 + 14.7) / 14.7 = 7.8

ACFM = SCFM / CR

Receiver Tank Size

V = T x C x 14.7 / (P1 - P2)

V = Volume (gallons)
T = Time (minutes)
C = CFM demand
P1, P2 = Cut pressures