NFPA in USA

NFPA 13 calculator

Velocity Pressure Calculator

Calculate sprinkler pipe velocity pressure from flow and internal diameter.

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

Velocity pressure

0.79 psi

Calculated output

Nominal pipe size3"
Pipe scheduleSchedule 40
Internal diameter3.068in
Velocity pressure0.79psi

NFPA in USA calculation workpaper

Velocity Pressure 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

Results

Nominal pipe size
3"
Pipe schedule
Schedule 40
Internal diameter
3.068 in
Velocity pressure
0.79 psi

Calculation basis

Formula
Pv = 0.001123 x Q^2 / d^4
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

Pv = 0.001123 x Q^2 / d^4

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

Density and Area Baseline

Hazard ClassificationDensity (GPM/sq ft)Design Area (sq ft)
Light Hazard0.101500
Ordinary Hazard Group 10.151500
Ordinary Hazard Group 20.201500
Extra Hazard Group 10.302500
Extra Hazard Group 20.402500

Use this result

Use velocity pressure as a hydraulic screening value for the selected pipe condition.

Check before use
Confirm flow and internal diameter are from the same pipe segment.
Common pitfall
Using velocity pressure without friction loss omits the controlling pipe-run pressure drop.
Next step
Hazen-Williams Friction Loss Calculator

Input evidence

Confirm these values before using the result.

  • Flow rate (GPM)
  • Nominal pipe size
  • Pipe schedule

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

Hazen-Williams Friction Loss CalculatorSprinkler K-Factor Flow and Pressure CalculatorNFPA 13 tool hubSprinkler Pipe Internal Diameter ReferenceNFPA 13 Design Density and Area Reference

FAQ

What is this Velocity Pressure 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.