What is the pipe-schedule method?

It is a prescriptive NFPA 13 shortcut that fixes pipe size by the maximum number of sprinklers a pipe may serve, rather than by calculating pressure and flow. It applies only to Schedule 40 steel pipe in pipe-schedule systems for light and ordinary hazard occupancies.

How many sprinklers can a 2 inch pipe feed?

Under both the light and ordinary hazard schedules, 2 inch Schedule 40 steel pipe may serve up to 10 sprinklers. A 1-1/2 inch pipe serves up to 5, and 2-1/2 inch jumps to 30 for light hazard or 20 for ordinary hazard.

When must I use hydraulic calculation instead?

The pipe-schedule method is limited to systems up to about 5,000 ft² and to specified materials. Larger systems, copper or CPVC pipe, and any modern hydraulically designed layout must be sized by full NFPA 13 hydraulic calculation, which this tool flags when the area exceeds the limit.

Why do light and ordinary hazard use different tables?

Ordinary hazard occupancies need more water per sprinkler because the fuel load is higher, so each pipe size carries fewer heads. A 2-1/2 inch pipe feeds 30 sprinklers at light hazard but only 20 at ordinary hazard for that reason.

Does this size copper or CPVC pipe?

No. The schedule shown is specifically for Schedule 40 steel pipe. Copper tube and CPVC have their own friction characteristics and are always sized by hydraulic calculation, never by this steel schedule table.

Fire Sprinkler Pipe Sizing Calculator (NFPA 13)

The NFPA 13 pipe-schedule method lets a sprinkler fitter size a system without running a full hydraulic calculation: pipe size is simply a function of how many sprinklers the pipe must feed. This calculator looks up the right Schedule 40 steel size and warns when the job has outgrown the schedule shortcut.

How it works

Each pipe size carries a maximum sprinkler count from the NFPA 13 light or ordinary hazard schedule:

light hazard:   1"→2  1-1/4"→3  1-1/2"→5  2"→10  2-1/2"→30  3"→60  3-1/2"→100
ordinary:       1"→2  1-1/4"→3  1-1/2"→5  2"→10  2-1/2"→20  3"→40  ...  6"→275
size = smallest pipe whose max ≥ sprinklers served

If the system coverage area exceeds roughly 5,000 ft², the pipe-schedule method no longer applies and NFPA 13 requires hydraulic design, which the tool flags.

Example and notes

A light-hazard branch line feeding 6 sprinklers needs 2-inch Schedule 40 steel, since 1-1/2 inch tops out at 5 and 2 inch covers up to 10. The same 6 heads on an ordinary-hazard system still land on 2-inch pipe, but the cross-main beyond it fills up faster because each ordinary-hazard size carries fewer heads. Use this for quick checks on small light-hazard jobs; anything larger, or built from copper or CPVC, must be hydraulically calculated.