NFPA in USA

NFPA 13 calculator

Pipe Sizing Calculator

Select a preliminary sprinkler pipe size from flow and target velocity limits.

Sprinkler SystemsNFPA 13Workpaper

Calculation workpaper

Enter inputs, review outputs, then use the guidance below before carrying the result forward.

US customary units

Calculation inputs

Enter project screening values in the units shown.

Ready

Worksheet header

Optional project fields for keeping the calculation screen traceable.

Results

Ready

Internal diameter

3.068 in

Calculated output

Target velocity

20 ft/s

Calculated output

Velocity within target

Pass

Pass/review state

Nominal pipe size3"
Pipe scheduleSchedule 40
Internal diameter3.068in
Target velocity20ft/s
Velocity within targetPass
Pipe velocity10.85ft/s

Before project use

Save the input source, formula, units, warnings, and result with the project record before carrying this screening value into design coordination or AHJ review.

Next calculator: Sprinkler Pipe Velocity Calculator

NFPA in USA calculation workpaper

Pipe Sizing Calculator

NFPA 13 ยท Sprinkler Systems

nfpainusa.comGenerated record

Project record

Project ID
Not entered
Area
Not entered
System
Not entered
Revision
Not entered
Prepared by
Not entered
Checked by
Not entered

Inputs

Flow rate
250 GPM
Nominal pipe size
3"
Pipe schedule
Schedule 40
Target maximum velocity
20 ft/s

Results

Nominal pipe size
3"
Pipe schedule
Schedule 40
Internal diameter
3.068 in
Target velocity
20 ft/s
Velocity within target
Pass
Pipe velocity
10.85 ft/s

Calculation basis

Formula
v = Q / (2.448 x d^2)
Reference standard
NFPA 13
Professional boundary
Verify adopted code, project criteria, listed equipment data, and AHJ requirements before relying on this record.
NFPA in USAnfpainusa.comThis is a calculation record, not a signed or sealed engineering document.

Calculation basis

Use the formula and linked reference data after the result is visible. Keep input selection separate from the calculation screen.

Formula

v = Q / (2.448 x d^2)

Nominal Pipe Diameter

Nominal SizeSchedule 10 ID (in)Schedule 40 ID (in)
3/4"0.8840.824
1"1.0971.049
1-1/4"1.4421.38
1-1/2"1.6821.61
2"2.1572.067
2-1/2"2.6352.469

Professional review path

Use this calculator as a workpaper step: collect evidence, make a review decision, then move the record into the next workflow.

Evidence to collect
  • Pipe segment flow assigned from the layout, demand estimate, or hydraulic node.
  • Nominal pipe size and schedule being screened for the same pipe segment.
  • Target velocity limit or project review criterion used for preliminary sizing.
Review decision
Decide whether the selected pipe size can move into Hazen-Williams friction-loss review or needs a larger diameter before hydraulic coordination.

Use this result

Use the velocity result to decide whether the selected pipe size needs review before hydraulic modeling.

Check before use
Confirm flow, schedule, and target velocity are appropriate for the pipe segment being screened.
Common pitfall
A velocity pass does not prove friction loss, pressure balance, or final pipe selection.
Next step
Hazen-Williams Friction Loss Calculator

Input evidence

Confirm these values before using the result.

  • Flow rate (GPM)
  • Nominal pipe size
  • Pipe schedule
  • Target maximum velocity (ft/s)

Authority basis

Check jurisdiction, AHJ, submittal, and edition records before using this result as project evidence.

State and Local Code Adoption WorkflowAHJ Contact ChecklistFire Protection Submittal ChecklistNFPA 13, 72, and 25 Edition Basis Worksheet

Record retention

Save the PDF after project fields, inputs, and results are set.

PDF includes

  • Project header and calculator inputs
  • Computed result rows and warnings
  • Formula, reference basis, and professional boundary

Check before filing

  • Input traceability
  • Method review
  • Output reasonableness
  • Professional boundary

Open next

NFPA 13 Hydraulic Design WorksheetSprinkler Pipe Internal Diameter ReferenceNFPA 13 Sprinkler System Calculators
Engineering disclaimer
NFPA in USA provides engineering workpapers, calculation checks, and reference tables for project screening and coordination. Final design decisions, code interpretations, submittals, and acceptance records must be completed by qualified professionals and verified against the adopted code, project criteria, listings, and Authority Having Jurisdiction requirements. This site does not issue signed or sealed engineering documents.

Related tools and tables

Pipe Velocity CalculatorHazen-Williams Friction Loss CalculatorNFPA 13 tool hubSprinkler Pipe Internal Diameter Reference

FAQ

What is this Pipe Sizing calculator for?+
Use it to compute a defined fire protection value from documented inputs, then retain the inputs, result, formula, and warnings with the project record.
Are the results suitable for permit submission?+
Use the saved record only after it is checked against adopted code, project criteria, equipment listings, and AHJ requirements.