NFPA in USA

NFPA 13 calculator

Sprinkler K-Factor Flow and Pressure Calculator

Solve sprinkler flow, pressure, or K-factor from the standard Q equals K times square root of pressure relationship used for sprinkler discharge checks.

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

K

5.6

Calculated output

Calculated value

28

Calculated output

Selected K-factorK5.6
K-factor useStandard spray
K5.6
Calculated value28

NFPA in USA calculation workpaper

Sprinkler K-Factor Flow and 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

Solve for
Flow
Listed K-factor
K5.6
Pressure
25 psi
Flow
28 GPM

Results

Selected K-factor
K5.6
K-factor use
Standard spray
K
5.6
Calculated value
28

Calculation basis

Formula
Q = K x sqrt(P)
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

Q = K x sqrt(P)

Standard K-Factors

K-FactorTypical UseNumeric K
K2.8Small orifice2.8
K5.6Standard spray5.6
K8.0Large orifice8
K11.2Extended coverage11.2
K14.0ESFR / storage14
K16.8Large drop / storage16.8

Use this result

Use calculated flow or pressure to screen a selected sprinkler discharge point.

Check before use
Confirm the listed K-factor and pressure basis come from the same sprinkler and design condition.
Common pitfall
Treating a K-factor screen as a full remote-area hydraulic calculation creates false confidence.
Next step
Sprinkler Density and Area Calculator

Input evidence

Confirm these values before using the result.

  • Solve for
  • Listed K-factor
  • Pressure (psi)
  • Flow (GPM)

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 WorksheetFire Sprinkler K-Factor TableNFPA 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

Sprinkler Density and Area CalculatorSprinkler System Demand CalculatorFire Sprinkler K-Factor Table

FAQ

What is this K-factor 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.