Reviewing a project’s pipe requirements begins with the size specified in the drawings and bill of quantities, then checking that size against the outside diameter, wall thickness, and required standard. This becomes especially important when site and procurement teams work with multiple diameters or pipe schedules within the same project.
A steel pipe size chart helps engineers, contractors, and procurement teams verify product details before ordering and receiving materials. In this article, we cover circular pipe dimensions, Schedule 40 wall thicknesses and weights, how to read sizes in inches and millimeters, and the information needed to source pipes, fittings, and flanges for your project.
Steel Pipe Size Chart
The following steel pipe size chart shows how nominal size in inches and DN relates to the outside diameter of circular pipes in the ASME B36.10 dimensional series. These figures are used to check nominal dimensions; actual products remain subject to the manufacturing tolerances specified by their applicable standard.
This chart is not an inventory list, nor does it specify the pipe wall thickness or material grade. Those details must be stated separately in the purchase request:
| Nominal Size (inches) | Nominal Size (DN) | Outside Diameter (mm) |
|---|---|---|
| 1/2 | 15 | 21.3 |
| 3/4 | 20 | 26.7 |
| 1 | 25 | 33.4 |
| 1 1/4 | 32 | 42.2 |
| 1 1/2 | 40 | 48.3 |
| 2 | 50 | 60.3 |
| 2 1/2 | 65 | 73.0 |
| 3 | 80 | 88.9 |
| 3 1/2 | 90 | 101.6 |
| 4 | 100 | 114.3 |
| 5 | 125 | 141.3 |
| 6 | 150 | 168.3 |
| 8 | 200 | 219.1 |
| 10 | 250 | 273.0 |
| 12 | 300 | 323.8 |
| 14 | 350 | 355.6 |
| 16 | 400 | 406.4 |
| 18 | 450 | 457.2 |
| 20 | 500 | 508.0 |
| 22 | 550 | 558.8 |
| 24 | 600 | 609.6 |
On mobile, swipe the table horizontally to view all columns when needed.
Schedule 40 Seamless Steel Pipe Size and Weight Chart
When ordering seamless pipes, wall thickness must be specified alongside the size. This Schedule 40 steel pipe size chart helps you check the outside diameter, wall thickness, and theoretical weight per meter before preparing a supply quotation.
The following weights are based on plain-end steel pipes. They are indicative theoretical figures, not confirmed shipment weights:
| Nominal Size (inches) | Outside Diameter (mm) | Wall Thickness (mm) | Approx. Weight (kg/m) |
|---|---|---|---|
| 1/2 | 21.3 | 2.77 | 1.27 |
| 3/4 | 26.7 | 2.87 | 1.69 |
| 1 | 33.4 | 3.38 | 2.50 |
| 1 1/4 | 42.2 | 3.56 | 3.39 |
| 1 1/2 | 48.3 | 3.68 | 4.05 |
| 2 | 60.3 | 3.91 | 5.44 |
| 2 1/2 | 73.0 | 5.16 | 8.64 |
| 3 | 88.9 | 5.49 | 11.29 |
| 4 | 114.3 | 6.02 | 16.08 |
| 5 | 141.3 | 6.55 | 21.77 |
| 6 | 168.3 | 7.11 | 28.26 |
| 8 | 219.1 | 8.18 | 42.55 |
| 10 | 273.0 | 9.27 | 60.30 |
| 12 | 323.8 | 10.31 | 79.72 |
On mobile, swipe the table horizontally to view all columns when needed.
How to Read Pipe Diameter Charts and Their Components
First, check the dimensional standard indicated above the chart, then find the row for the required pipe size. The following fields help you match the steel pipe size chart to your project requirements:
1. Nominal Pipe Size
Identify the size in inches or DN exactly as shown in the drawing or bill of quantities, then locate it in the chart. Remember that nominal size identifies a pipe within a dimensional series; it is not necessarily a direct measurement of the inside diameter.
2. Outside Diameter
Read the outside diameter from the same row and use it to check the pipe dimensions and corresponding components, allowing for the tolerances specified in the standard.
This comparison helps avoid confusing nominal size with a measured dimension, especially when information passes between engineering, purchasing, and warehouse teams.
3. Wall Thickness
Specify the required pipe schedule or wall thickness, then check the figure for the chosen size. Wall thickness within a given schedule varies from one diameter to another.
A pipe specification must include both size and wall thickness. Asking for a 3-inch pipe without stating its wall thickness or schedule is not sufficient.
4. Weight and Length
Use the theoretical weight per meter to estimate the order weight, then multiply by the required lengths. Check whether the bill of quantities specifies the number of pieces, total meters, or particular lengths.
The actual weight may differ from the theoretical estimate within permitted tolerances. End preparations and coatings also need to be considered separately when calculating shipment weight.
Steel Pipe Diameters in Millimeters and Inches
Nominal pipe size is different from converting units of measurement. One inch equals 25.4 mm as a unit of length, but the nominal pipe size in inches cannot simply be converted to obtain the pipe’s outside diameter.
A 3-inch pipe illustrates the difference: converting 3 inches directly gives 76.2 mm, while its nominal outside diameter is 88.9 mm in the dimensional series used in this steel pipe size chart.
Direct conversion is appropriate when the figure is an actual measured dimension, such as a piece length or a diameter measured with a tool. Matching a nominal size, however, requires the dimensional chart for the relevant product standard.
Recording nominal size and outside diameter in separate columns of the material list makes checking easier, especially when a bill of quantities includes pipes and accessories with similar nominal sizes.
The Difference Between Schedule 40 and STD Steel Pipe
Schedule 40 and STD are both used in some steel pipe orders. Their wall thicknesses match through 10-inch nominal pipe size in the relevant steel pipe dimensional series, but differ at larger sizes.
A 12-inch pipe shows why the wording matters: STD wall thickness is approximately 9.53 mm, while Schedule 40 wall thickness is approximately 10.31 mm. The designation in the bill of quantities should therefore be reproduced accurately.
XS and Schedule 80 must also be checked. Their thicknesses match through 8-inch nominal pipe size in the same series, but differ at certain larger diameters.
Using a steel pipe size chart helps prevent acceptance of a non-equivalent substitute, especially when one order includes both small and large diameters.
How to Choose Matching Pipe Fitting and Flange Sizes
When checking a steel pipe size chart, the fittings used on the line must also match. The same nominal designation does not, by itself, guarantee that every connection component is compatible. The following details help prepare an accurate order:
1. Specify the Fitting Size and Type
Specify the size of each elbow, tee, reducer, or cap, then check its standard, connection method, and material. For reducers, record both required end sizes rather than only one.
The wall thickness of butt-weld fittings, their end preparation, and compatibility with the pipe must be checked against the approved design and specifications.
2. Check Flange Specifications
Specify the flange type, nominal size, pressure class, material, facing, and standard. For flanges where pipe wall thickness affects the bore, check the relevant internal dimensions.
A flanged joint also requires a suitable gasket and bolts for the design and operating conditions, so it is advisable to include these in the bill of quantities.
3. Verify the Thread Type
Specify the thread type and size when ordering threaded fittings, then confirm compatibility with the mating component. Matching nominal sizes alone does not guarantee that different thread systems will fit together.
Checking each fitting’s type, rating, and material helps prepare a quotation covering the pipes and fittings required for each item.
Using the Correct Pipe Measuring Tools
Dimensional checks during receipt help compare delivered products with the bill of quantities and the manufacturer’s documents. Measurements should follow the approved inspection procedures, including the following steps:
1. Review Product Identification
Check the size, standard, grade, and pipe schedule against the available documents and product markings. Then identify the required values in the steel pipe size chart.
Measurements alone do not establish the material grade or test results. The manufacturer’s test certificate and other required documents remain part of the product review.
2. Measure the Outside Diameter
Use a measuring tool suitable for the diameter range, clean the contact area before taking a reading, and compare the result with the nominal dimension and the tolerances specified in the product standard.
3. Measure Wall Thickness
Use a measuring tool suitable for the inspection point and condition of the pipe. Account for any coating or beveled ends, and record the readings according to the approved inspection plan.
4. Verify Lengths and Quantities
Check the number of pieces, length of each item, and total linear meters. Confirm that delivered lengths comply with the purchase terms, and record the findings and any discrepancies requiring review.
Source Seamless Steel Pipe Sizes for Your Project with GTS
Accurate sourcing begins with a list of required sizes, wall thicknesses, standards, and quantities. Global Trading Supplies (GTS) accepts project bills of quantities for seamless carbon steel pipes, fittings, and flanges.
The company offers pipes of Ukrainian, Russian, and Chinese origin, as well as threaded fittings, high-pressure fittings, butt-weld fittings, and flanges. Engineers, contractors, and procurement teams can inquire about available products, technical documents, and delivery dates.
Required sizes and quantities are reviewed when the inquiry is submitted. Published dimensional charts are intended to identify pipe dimensions and do not mean that every item is currently in stock.
Conclusion
A steel pipe size chart helps match item descriptions with nominal diameters, wall thicknesses, and theoretical weights. It becomes even more useful when dimensions are considered alongside the standard, material grade, piece length, and required connection components.
Check fitting and flange details and the technical documentation before approving an order. Then compare delivered products with the purchase terms and inspection plan to ensure your project receives the required sizes.
Frequently Asked Questions
How Do You Read Pipe Diameter Charts Correctly?
Identify the chart standard and nominal pipe size, then follow the corresponding row to find the outside diameter, wall thickness, and weight, where available. Check the unit used for each column.
Does the Pipe Size in Inches Equal Its Outside Diameter?
Not necessarily. Nominal pipe size is a designation within a dimensional series, so you must consult the applicable chart to find the corresponding outside diameter.
Does DN Represent the Actual Inside Diameter of a Pipe?
DN is a nominal size designation. The actual inside diameter depends on the outside diameter and wall thickness, so the DN number alone must not be treated as the measured bore.
Does the Outside Diameter Change with the Pipe Schedule?
For the same nominal size within one dimensional series, the nominal outside diameter remains constant, while wall thickness and inside diameter change. Actual dimensions are subject to manufacturing tolerances.
Is Schedule 40 the Same as STD for All Pipe Sizes?
They match through 10-inch nominal size in the relevant steel pipe dimensional series, but wall thicknesses differ at larger sizes. Always check the specified product designation.
Do Pipes Made from Different Materials Have the Same Diameters?
Pipe dimensional series vary by material and manufacturing standard. Compare sizes using the applicable product chart and specification rather than relying on the nominal name alone.
