NFPA in USA

Conversion calculator

Pipe Dimension Reference Calculator

Lookup nominal pipe size and internal diameter values for quick calculation setup.

Unit ConversionConversionWorkpaper

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

Selected internal diameter

3.068 in

Calculated output

Schedule 10 ID

3.26 in

Calculated output

Schedule 40 ID

3.068 in

Calculated output

Nominal pipe size3"
Pipe scheduleSchedule 40
Selected internal diameter3.068in
Schedule 10 ID3.26in
Schedule 40 ID3.068in

Engineering notes

  • Confirm final internal diameter from the pipe manufacturer and selected pipe specification.

NFPA in USA calculation workpaper

Pipe Dimension Reference Calculator

Conversion ยท Unit Conversion

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

Nominal pipe size
3"
Pipe schedule
Schedule 40

Results

Nominal pipe size
3"
Pipe schedule
Schedule 40
Selected internal diameter
3.068 in
Schedule 10 ID
3.26 in
Schedule 40 ID
3.068 in

Calculation basis

Formula
Internal diameter selected by nominal size and schedule
Reference standard
Conversion
Professional boundary
Verify adopted code, project criteria, listed equipment data, and AHJ requirements before relying on this record.

Warnings and notes

  • Confirm final internal diameter from the pipe manufacturer and selected pipe specification.
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

Internal diameter selected by nominal size and schedule

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

Use internal diameter values for velocity, friction loss, and velocity pressure calculators.

Check before use
Confirm nominal size and schedule match the pipe material and calculation scenario.
Common pitfall
Nominal pipe size is not the internal diameter used in hydraulic formulas.
Next step
Hazen-Williams Friction Loss Calculator

Input evidence

Confirm these values before using the result.

  • Nominal pipe size
  • Pipe schedule

Authority basis

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

AHJ Contact 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 ReferenceFire Protection Calculator Library
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

Calculator librarySprinkler Pipe Internal Diameter Reference

FAQ

What is this Pipe Dimension Reference 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.