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Interactive Mechanical Engineering Reference

Pipe Size Chart

Look up common steel pipe dimensions by NPS, DN, and schedule. Compare outside diameter, nominal wall thickness, calculated inside diameter, and flow area in U.S. customary or metric units.

  • Basis: ASME B36.10 dimensional system
  • Range: Common NPS 1/2 through 8
  • Schedules: 40 and 80
  • Use: Dimensional reference, not pressure design

Dimension selector and live cross-section

Interactive Pipe Size and Schedule Lookup

Choose a nominal size and schedule to see the actual outside diameter and calculated bore.

NPS 2 · DN 50 · Schedule 40 Common wrought-steel dimensional excerpt
Outside diameter2.375 inSource-controlled nominal dimension
Wall thickness0.154 inSource-controlled nominal dimension
Inside diameter2.067 inCalculated as OD − 2t
Internal flow area3.356 in²Calculated as πID² ÷ 4
NPS 2 Schedule 40 pipe cross-section Proportional pipe cross-section showing a 2.375 inch outside diameter, 2.067 inch calculated inside diameter, and 0.154 inch nominal wall thickness. OD 2.375 in ID 2.067 in t = 0.154 in NPS 2 DN 50 Schedule 40 Proportional cross-section Not actual physical size
The drawing preserves the selected OD-to-ID ratio. It is proportional, not a printable full-size template.
Schedule is not a pressure rating

Schedule identifies a dimensional wall series. Allowable pressure also depends on material specification, temperature, manufacturing tolerance, corrosion allowance, joining method, applicable piping code, and project conditions.

Server-rendered dimensional reference

Pipe Size and Schedule Dimensions

26 common steel-pipe size and schedule rows

Find a size: search NPS or DN, filter by schedule, select up to four rows for comparison, or choose View to send a row to the diagram.

Limited educational excerpt of common wrought-steel NPS sizes and Schedule 40/80 dimensions. OD and wall are published nominal dimensions; ID and flow area are calculated. Consult the official ASME standard and project specifications for authoritative design.
SelectPipe dimensions (in)Action
NPS 1/2DN 15Schedule 400.840 in0.109 in0.622 in0.304 in²
NPS 1/2DN 15Schedule 800.840 in0.147 in0.546 in0.234 in²
NPS 3/4DN 20Schedule 401.050 in0.113 in0.824 in0.533 in²
NPS 3/4DN 20Schedule 801.050 in0.154 in0.742 in0.432 in²
NPS 1DN 25Schedule 401.315 in0.133 in1.049 in0.864 in²
NPS 1DN 25Schedule 801.315 in0.179 in0.957 in0.719 in²
NPS 1-1/4DN 32Schedule 401.660 in0.140 in1.380 in1.496 in²
NPS 1-1/4DN 32Schedule 801.660 in0.191 in1.278 in1.283 in²
NPS 1-1/2DN 40Schedule 401.900 in0.145 in1.610 in2.036 in²
NPS 1-1/2DN 40Schedule 801.900 in0.200 in1.500 in1.767 in²
NPS 2DN 50Schedule 402.375 in0.154 in2.067 in3.356 in²
NPS 2DN 50Schedule 802.375 in0.218 in1.939 in2.953 in²
NPS 2-1/2DN 65Schedule 402.875 in0.203 in2.469 in4.788 in²
NPS 2-1/2DN 65Schedule 802.875 in0.276 in2.323 in4.238 in²
NPS 3DN 80Schedule 403.500 in0.216 in3.068 in7.393 in²
NPS 3DN 80Schedule 803.500 in0.300 in2.900 in6.605 in²
NPS 3-1/2DN 90Schedule 404.000 in0.226 in3.548 in9.887 in²
NPS 3-1/2DN 90Schedule 804.000 in0.318 in3.364 in8.888 in²
NPS 4DN 100Schedule 404.500 in0.237 in4.026 in12.730 in²
NPS 4DN 100Schedule 804.500 in0.337 in3.826 in11.497 in²
NPS 5DN 125Schedule 405.563 in0.258 in5.047 in20.006 in²
NPS 5DN 125Schedule 805.563 in0.375 in4.813 in18.194 in²
NPS 6DN 150Schedule 406.625 in0.280 in6.065 in28.890 in²
NPS 6DN 150Schedule 806.625 in0.432 in5.761 in26.067 in²
NPS 8DN 200Schedule 408.625 in0.322 in7.981 in50.027 in²
NPS 8DN 200Schedule 808.625 in0.500 in7.625 in45.664 in²

Data scope: common NPS 1/2 through 8 steel-pipe dimensions for Schedules 40 and 80 only. Stainless S schedules, other B36.10 schedules, PVC, copper tube, HDPE, ductile iron, tolerances, pressure ratings, and product availability are outside this table.

Table actions and selection controls

Bulk CSV download is intentionally unavailable because the controlling ASME dimensional table is copyrighted. Copy only the limited row needed and verify it against the official standard or approved project documentation.

Selected-row comparison

Compare Pipe Dimensions by Size and Schedule

The default compares Schedule 40 and Schedule 80 at NPS 2. Select other table rows to compare up to four combinations.

Selected rows2Maximum four
Active dimensions3OD, wall, and ID
Displayed range—Current unit system

Select pipe rows in the table to compare OD, wall thickness, and calculated ID.

Key Takeaways

  • NPS is a designation: A nominal 2-inch pipe has a 2.375-inch outside diameter in this dimensional system.
  • OD stays fixed by NPS: Schedule 80 increases wall thickness and reduces ID compared with Schedule 40 at the same nominal size.
  • Use actual ID for hydraulics: Flow area, velocity, capacity, and friction calculations depend on the bore, not the nominal label.
  • Keep material systems separate: Steel NPS, stainless S schedules, PVC schedules, copper tube types, and HDPE SDR are not one interchangeable table.

Important Pipe Size Chart Limitations

Do not use the chart as pressure or material approval

The displayed OD and wall values are nominal dimensional references for a limited set of common steel-pipe sizes. They do not establish allowable pressure, corrosion allowance, mill tolerance, material grade, product availability, code compliance, or fitness for a specific fluid service.

Method and terminology

How to Use and Interpret the Pipe Size Chart

Separate the nominal designation from the dimensions used in fabrication and fluid calculations.

  1. Select NPS or DN. The two selectors represent synchronized nominal designations, not measured diameters.
  2. Select the dimensional schedule. Schedule changes nominal wall thickness for the chosen NPS.
  3. Read OD and wall from the row. These are the source-controlled nominal dimensions used by the page.
  4. Use the calculated ID and area carefully. The results use nominal values and exclude tolerance, lining, deposits, corrosion, and ovality.
  5. Continue with the actual engineering task. Use ID in a pipe-flow or pipe-volume calculation, then verify the governing piping code and project specification.

NPS, DN, OD, ID, and Schedule

NPS
Nominal Pipe Size, a standardized size designation used for pipe and matching components.
DN
Diameter Nominal, the metric nominal designation defined for pipework components. It is not an exact measured millimeter diameter.
OD
Outside diameter, the physical diameter used for fit-up, clearances, supports, and many fabrication checks.
ID
Inside diameter, calculated here from nominal OD and wall thickness and used for bore-related calculations.
Schedule
A dimensional wall-thickness series tied to NPS. The same schedule number does not represent one universal wall thickness.
Wall thickness, t
The nominal radial thickness between outside surface and bore. Actual manufactured values are subject to permitted tolerances.

Why Schedule Changes Flow Area

At a fixed NPS, Schedule 40 and Schedule 80 share the same nominal OD in this table. The thicker Schedule 80 wall moves inward, reducing ID. Because area varies with the square of ID, a moderate bore reduction can create a larger percentage change in flow area and pipe capacity.

Reverse Lookup Limitations

A measured outside diameter can identify likely NPS candidates, but OD generally cannot identify schedule because schedules at the same NPS share the same nominal OD. Coatings, corrosion, measurement method, out-of-roundness, and manufacturing tolerance can also shift a field measurement.

Worked dimensional examples

Pipe Size Chart Examples

NPS 2 Schedule 40 Inside Diameter

Given: OD = 2.375 in and nominal wall thickness = 0.154 in.

Method: ID = 2.375 − 2(0.154).

Result: Calculated nominal ID = 2.067 in, with an internal area of about 3.356 in².

Check: Use manufacturer tolerances and the project specification when a minimum bore is critical.

NPS 2 Schedule 40 vs. Schedule 80

Given: Both rows use a 2.375 in nominal OD. Schedule 40 wall is 0.154 in; Schedule 80 wall is 0.218 in.

Result: Calculated ID decreases from 2.067 in to 1.939 in, and nominal internal area decreases by about 12.0%.

Interpretation: At equal volumetric flow, the smaller Schedule 80 bore would produce higher average velocity before friction and fitting effects are evaluated.

Scope and failure prevention

Pipe Dimension Selection Guidance and Common Mistakes

Use this chart for

  • Common steel NPS and DN lookup.
  • Schedule 40 and 80 dimensional comparison.
  • Preliminary clearances, bore geometry, and calculator inputs.

Verify separately

  • Material grade, specification, and temperature.
  • Pressure design, corrosion allowance, and wall tolerance.
  • Fitting bore, lining, joining system, and manufacturer availability.

Do not mix with

  • PVC or CPVC schedule tables.
  • Copper water tube Types K, L, or M.
  • HDPE SDR, ductile-iron classes, or tubing OD systems.

Common Pipe Size Chart Mistakes

  • Treating NPS as the actual inside or outside diameter.
  • Converting NPS directly to millimeters instead of using the associated DN designation.
  • Assuming Schedule 40 has one wall thickness for every pipe size.
  • Using outside diameter to calculate fluid capacity.
  • Assuming Schedule 80 automatically provides a known pressure rating without material and temperature data.
  • Using a carbon-steel schedule row for PVC, copper, HDPE, or another dimensional system.

Pipe Size Chart Sources, Scope, and Data Rights

Common wrought-steel NPS dimensions · Schedules 40 and 80 · Dataset version 1.0

This page publishes a limited educational dimensional excerpt and original derived calculations. It does not reproduce the complete ASME B36.10 table and does not provide a bulk standards-derived download.

Dataset and Review Details

Primary standard basis
ASME B36.10-2022
Displayed scope
Common NPS 1/2–8, Schedules 40 and 80
Source-controlled fields
NPS, DN mapping, nominal OD, and nominal wall thickness
Calculated fields
Nominal ID and internal cross-sectional area
Known exclusions
Other schedules, S schedules, tolerances, pressure ratings, material grades, and non-steel systems
Last reviewed
Reviewer
Turn2Engineering Editorial Team
Rights status
Limited educational excerpt; complete ASME table and bulk CSV not distributed
Dataset version
Pipe Size Reference 1.0
Rounding
Inch dimensions shown to 0.001 in; metric conversions shown to 0.01 mm
Parent Hub
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Frequently Asked Questions

No. NPS is a nominal designation. Actual nominal inside diameter changes with wall thickness, so the same NPS has a smaller calculated ID at Schedule 80 than at Schedule 40.

Pipe Size Chart Summary

Use the selector to connect an NPS or DN designation to a common Schedule 40 or Schedule 80 steel-pipe cross-section. Read OD and nominal wall thickness from the reference row, then use the clearly labeled calculated ID and flow area for preliminary geometric checks.

For final design, verify the complete current standard, material specification, manufacturing tolerance, piping code, project conditions, and approved product data. Continue to the Pipe Flow Calculator or Pipe Volume Calculator when the next task depends on actual bore size.

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