NFPA in USA

NFPA 13 calculator

Hazen-Williams Friction Loss Calculator

Calculate sprinkler pipe friction loss, total pressure loss, pipe velocity, and velocity pressure using the Hazen-Williams equation for water-based fire protection systems.

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

Hazen-Williams C value

140

Calculated output

Internal diameter

3.068 in

Calculated output

Friction loss

0.056 psi/ft

Calculated output

Pipe materialSteel (new)
Hazen-Williams C value140
Nominal pipe size3"
Pipe scheduleSchedule 40
Internal diameter3.068in
Friction loss0.056psi/ft
Total loss5.62psi
Pipe velocity10.85ft/s
Velocity pressure0.79psi

NFPA in USA calculation workpaper

Hazen-Williams Friction Loss Calculator

NFPA 13 ยท Sprinkler Systems

nfpainusa.comGenerated record

Project record

Project ID
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Area
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System
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Revision
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Prepared by
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Checked by
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Inputs

Flow rate
250 GPM
Nominal pipe size
3"
Pipe schedule
Schedule 40
Pipe length
100 ft
Pipe material
Steel (new)
Equivalent fitting length
0 ft

Results

Pipe material
Steel (new)
Hazen-Williams C value
140
Nominal pipe size
3"
Pipe schedule
Schedule 40
Internal diameter
3.068 in
Friction loss
0.056 psi/ft
Total loss
5.62 psi
Pipe velocity
10.85 ft/s
Velocity pressure
0.79 psi

Calculation basis

Formula
Pf = 4.52 x Q^1.85 / (C^1.85 x d^4.87)
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

Pf = 4.52 x Q^1.85 / (C^1.85 x d^4.87)

Common C Values

Pipe MaterialC Value
Steel (new)140
Steel (old or galvanized)100
Copper150
CPVC150
Black steel dry system100
Cast iron100

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

Use this result

Carry total loss and velocity into the system demand or pipe sizing review.

Check before use
Confirm C value, internal diameter, pipe schedule, and equivalent length match the same pipe run.
Common pitfall
Using nominal diameter instead of internal diameter will understate friction loss.
Next step
Sprinkler System Demand Calculator

Input evidence

Confirm these values before using the result.

  • Flow rate (GPM)
  • Nominal pipe size
  • Pipe schedule
  • Pipe length (ft)
  • Pipe material
  • Equivalent fitting length (ft)

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 WorksheetHazen-Williams C Values for Fire Sprinkler PipeNFPA 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 CalculatorSprinkler System Demand CalculatorSprinkler Pipe Internal Diameter ReferenceHazen-Williams C Values for Fire Sprinkler PipeEquivalent Pipe Lengths for Common Fittings

FAQ

What is this Hazen-Williams 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.