Pipes Schedule Chart

Nominal Bore Size Chart (NB Pipe Size Chart)

This pipe NB chart is the quickest way to read NB size, inch size and OD together. It lists the most used nominal bore pipe sizes.

NB to Inch Converter: Common Pipe Sizes

Use this quick NB-to-inch conversion chart to find the corresponding nominal pipe size in inches. These are standard nominal size equivalents, not actual pipe diameter measurements.

Note: NB and inch values refer to nominal pipe sizes. The actual outside diameter depends on the standard size designation, not a direct conversion from inches to millimetres.

Inch to NB Conversion Chart

NB to MM Chart

An NB value in mm is just the DN number. What you actually need is the OD in mm. ASME and EN (ISO) standards differ slightly on some sizes.

Always confirm which standard your project follows. A 65 NB pipe can be 73.0 mm or 76.1 mm, and fittings made for one will not fit the other.

NB Pipe OD Chart (Pipe OD Chart)

The OD stays the same in every schedule. Only the wall thickness changes. Here are the answers people search for most:

• 32 NB pipe OD: 42.2 mm
• 40 NB pipe OD: 48.3 mm
• 50 NB pipe OD: 60.3 mm
• 80 NB pipe OD: 88.9 mm
• 100 NB pipe OD: 114.3 mm
• 150 NB pipe OD: 168.3 mm
• 250 NB pipe OD: 273.1 mm

Standard Pipe Sizes in mm for Large Pipes

For 26 inch and above, the OD in mm is the inch size multiplied by 25.4.

DN to NPS for very large sizes:

NB Pipe Schedule Chart (Pipe Schedule Chart in mm)

Schedule sets the wall thickness. A higher schedule means a thicker wall and a smaller bore. These are carbon steel values in mm per ASME B36.10M.

Sch 10 to Sch 80:

Sch 100 to XXS:

Two rules to remember. STD equals Sch 40 only up to 10 inch, and XS equals Sch 80 only up to 8 inch. For bigger pipes, quote the schedule number or the wall in mm.

Large pipe walls (26" to 36"), in mm:

Stainless Steel Pipe Schedule Chart (5S, 10S, 40S, 80S)

Stainless pipes follow ASME B36.19M and use thinner "S" schedules. Wall thickness in mm:

NB Pipe Dimensions for Popular Sizes

Each table below shows wall, inside diameter (ID) and weight for carbon steel, plain end. Weight uses (OD − Wall) × Wall × 0.02466.

Find 1/2 Inch Nominal Bore Pipe Dimensions (1/2 NB Pipe, 15 NB)

The 1/2 inch NB pipe has an OD of 21.3 mm (0.840 inch) in every schedule.

Common uses for the 1/2 inch NB pipe include instrument lines, sampling points and small utility lines.

10 NB Pipe Size (3/8 Inch, OD 17.1 mm)

20 NB Pipe Size (3/4 Inch, OD 26.7 mm)

25 NB Pipe Size (1 Inch, OD 33.4 mm)

32 NB Pipe Size (1 1/4 Inch, OD 42.2 mm)

40 NB Pipe Dimensions (NB 40 Pipe Size, 1 1/2 Inch, OD 48.3 mm)

50 NB Pipe Size (2 Inch, OD 60.3 mm)

80 NB Sch 80 Pipe Dimensions (3 Inch, OD 88.9 mm)

For 80 NB in Sch 80, the wall is 7.62 mm (0.300 inch), the ID is 73.7 mm, and the weight is 15.27 kg/m (10.26 lb/ft).

NB 100 Pipe Dimensions (4 Inch, OD 114.3 mm)

150 NB Pipe Dimensions (6 Inch, OD 168.3 mm)

250 NB Pipe Dimensions (10 Inch, OD 273.1 mm)

NB Pipe Weight Chart (kg per Metre)

Use this NB pipe weight chart to estimate freight, support loads and material cost. Values are for carbon steel, plain end, per ASME B36.10M.

Weight formula: Weight (kg/m) = (OD − Wall) × Wall × 0.02466 for carbon and low-alloy steel. Use 0.02491 for 304 stainless steel. OD and wall are in mm.

Example for 50 NB Sch 40: (60.3 − 3.91) × 3.91 × 0.02466 = 5.44 kg/m.

Mill weight can differ a little because of wall tolerance, which is typically −12.5% on seamless pipe. To convert kg/m to lb/ft, multiply by 0.672.

Seamless Steel Pipe Dimensions

Seamless pipe has no weld seam. It is sized by NB and schedule, so every OD and wall value in the charts above applies to it. It is the usual choice for high-pressure and high-temperature lines.

Seamless Steel Tube Dimensions

Tubes are sized by actual OD and wall thickness, not by NB. This is the main difference from pipe. Tubes suit instrumentation, heat exchangers and hydraulic lines, where tight tolerance matters.

Imperial tubes (304/316 stainless, weight in kg/m):

Metric tubes:

Custom OD and wall combinations are available on request.

IS 1239 Pipe Sizes (Light, Medium and Heavy)

Indian water, gas and steam pipes under IS 1239 (Part 1) use light, medium and heavy classes instead of schedules. Typical wall thickness in mm:

Please check the latest edition of IS 1239 before ordering, as tolerances and values are revised from time to time.

Pipe vs Tube: Quick Difference

Pipes and tubes may look similar, but they serve different purposes. Pipes are mainly used to transport fluids and gases, while tubes are often used where precise dimensions and tighter tolerances are important.

Example: A 50 NB pipe has a standard outside diameter of 60.3 mm. A tube specified as 50 mm OD has an actual outside diameter of 50 mm.

Always check the applicable ASTM, ASME, or other product standard when selecting pipes or tubes, as dimensions and tolerances vary by specification.

How to Read Any NB Pipe Size Chart

An NB pipe size chart helps you find a pipe’s nominal size, outside diameter, wall thickness, and weight. Follow these steps to identify the correct dimensions for your application.

• Find the NB size: Locate the nominal bore, such as 25 NB, 50 NB, or 100 NB.
• Check the inch equivalent: Match the NB size with its corresponding NPS designation, such as 50 NB = 2 inches.
• Confirm the outside diameter (OD): Check the standard OD for that nominal size. For example, a 50 NB pipe has an OD of 60.3 mm.
• Select the pipe schedule: Choose the required wall thickness, such as Schedule 10, 40, or 80. A higher schedule generally means a thicker wall for the same nominal size.
• Check the wall thickness: Read the thickness in millimetres against the selected pipe size and schedule.
• Find the pipe weight: Use the chart’s weight column to estimate the weight per metre or per foot.
• Verify the applicable standard: Check whether the dimensions follow ASME B36.10M for many carbon and alloy steel pipes or ASME B36.19M for stainless steel pipes.

Example: For a 50 NB (NPS 2) pipe, the standard OD is 60.3 mm. The wall thickness and inside diameter depend on the selected schedule.

Where Common NB Pipe Sizes Are Used

Different nominal bore (NB) sizes suit different flow rates and piping requirements. The following guide shows common applications across industrial systems.

• 15 to 25 NB: Instrument air, sampling lines, chemical dosing, and utility water.
• 40 to 80 NB: Process branches, cooling water, firefighting systems, and fuel lines.
• 100 to 200 NB: Main process headers, steam lines, and pump suction and discharge lines.
• 250 to 600 NB: Large pipelines, power plant cooling water systems, and oil and gas applications.

The final pipe size depends on flow rate, pressure, temperature, material, and system design. These ranges are general examples, not fixed rules for every application.

NB Pipes and Fittings Supply

We supply seamless and welded pipes and tubes in carbon steel, stainless steel, alloy steel, duplex, and nickel alloys. Matching flanges and pipe fittings are available in different NB sizes, schedules, and material grades to suit your piping requirements.

With export experience across 85+ countries, we provide EN 10204 3.1 material test certificates as agreed for each order. Cut-to-length options and custom wall thicknesses can also be arranged, subject to material specifications and availability. To check availability and pipe weight, share your required NB size, schedule, material grade, and quantity.