Medical Gas Pipe Sizing Calculator

This simplified calculator sizes purely from Number of Outlets, Flow Rate per Outlet, and the outlet-count diversity factor -- Gas Type only sets the label shown next to your results. If you switch from Oxygen to Medical Air, remember to also raise Flow Rate per Outlet to reflect that gas's typically higher per-outlet demand, or the sizing will not change.

The diversity factor defined in NFPA 99, Health Care Facilities Code (referenced in its Table 5.1.11 for medical gas pipe sizing), steps down at 5, 12, and 24 outlets (from 1.0 to 0.8 to 0.6 to 0.5), reflecting that not all outlets flow at once on a larger system. Crossing one of those thresholds can lower total design flow even though you added an outlet, because the factor drop outweighs the extra outlet's demand.

Flow Rate per Outlet multiplies directly into Total Design Flow and Est. Pressure Drop with no diversity stepping applied to it, so it behaves as a straightforward linear scaling factor across its full 1 to 200 LPM range, unlike Number of Outlets.

Branch Pipe Size is selected from a fixed table of standard sizes based on ranges of total flow in CFM (up to 1, 3, 8, 15, or 30 CFM per size step). A modest change in outlet count or flow rate often still lands within the same bracket, so the recommended size only moves once the required flow crosses into the next bracket.