Pipe Size Chart: NB to Inches, OD & Weight

50 NB, 250 NB and 300 NB to inches: quick answers

Nominal inch names identify a pipe size; they are not a direct conversion of measured OD. These values follow the ASME pipe series used in the chart below.

Is 60.3 mm equal to 2 inches?

As a physical measurement, 60.3 mm ÷ 25.4 = approximately 2.374 inches. In nominal pipe terminology, an OD of 60.3 mm identifies NPS 2 / 50 NB in this series. A 2-inch nominal pipe and a tube with actual 2-inch OD are different products.

View all 15 NB to 300 NB sizes, schedules and weights ↓

Find your pipe. Compare options. Build an enquiry.

Use metric or imperial measurements, enter a supplier rate in your chosen currency, and collect several pipe sizes in one enquiry. Start with the finder or select the details below.

Four pipe sizes at a glance

ASME pipe series reference. Sizes are displayed as cards, not drawn to a common scale.

NB to inch pipe size chart, thickness & weight

Reference sizes below follow the ASME pipe series, covering 15 NB to 300 NB. Dimensions were cross-checked against published supplier reference tables listed below. We calculate weights from nominal OD, wall thickness and density; these are estimates, not measured shipment weights.

Showing 15 of 15 sizes. Scroll tables sideways on smaller screens.

MS / carbon steel: SCH 40 and SCH 80

SS304 / 304L: SCH 10S and SCH 40S

Carbon-steel weights use 7,850 kg/m³; SS304/304L weights use an assumed 7,930 kg/m³. For SS316/316L and other alloys, select the appropriate grade in our calculator. At 300 NB, SCH 40 is 10.31 mm while SCH 40S is 9.53 mm: do not omit the “S” when specifying stainless pipe.

Download printable PDF chart

Download the complete Steel Gems reference chart (CSV) · Open the weight calculator →

What are NB, DN, NPS, OD and ID?

• NB / DN: nominal size designations commonly used in enquiries; they do not state the measured bore.
• NPS: nominal pipe size, commonly described using inch-based trade names.
• OD: outside diameter; normally fixed for a given NPS in the same dimensional series.
• ID: inside diameter; approximately OD minus twice the wall thickness.
• Schedule: a wall-thickness designation that depends on pipe size and standard.

For example, 50 NB SCH 40 has nominal ID 60.3 − (2 × 3.91) = 52.48 mm. SCH 80 at the same size has nominal ID 49.22 mm. Read our SCH 40 vs SCH 80 selection guide for the engineering implications.

See the difference between OD, wall and bore

When wall thickness increases at the same nominal pipe size, OD stays fixed and the usable bore becomes smaller. That affects weight and flow area.

Pipe weight calculation formula

Weight (kg/m) = π × (OD − t) × t × density ÷ 1,000,000

Enter OD and thickness t in mm, and density in kg/m³. Multiply by length in meters for weight per piece, then by quantity for total weight. This estimates a plain hollow cylinder; it excludes coatings, couplings and attachments.

Actual supply weight can differ because of dimensional tolerances and manufacturing variation. Verify the applicable material standard, mill data and agreed billing basis.

How to convert ₹/kg into ₹/meter

₹/meter = theoretical kg/m × quoted ₹/kg. If a 50 NB SCH 40 carbon-steel pipe is quoted at an illustrative ₹75/kg, its estimated basic rate is 5.44 × ₹75 ≈ ₹407.81/meter. One 6-meter length is approximately ₹2446.87.

₹75/kg is a worked example, not a Steel Gems offer or current market price. Taxes, freight, testing and other charges depend on the quotation. Agree whether billing is by actual weight, nominal weight, meters or pieces.

ASME schedules and IS 1239 classes

ASME B36.10 and B36.19 are dimensional references for wrought steel and stainless pipe respectively. IS 1239 light, medium and heavy class pipes use their own requirements. Do not assume Class B equals SCH 40, or apply this chart to every Indian-standard pipe without checking the ordered standard.

Seamless and welded describe manufacture; SCH 40 describes dimensions. State both in an RFQ. Tubes ordered by actual OD × wall thickness also need a different approach from nominal pipe-size trade names.

Frequently asked pipe-size questions

50 NB is how many inches?

50 NB / DN50 corresponds to NPS 2, commonly called a 2-inch pipe, with nominal OD 60.3 mm in the ASME pipe series.

250 NB is how many inches?

250 NB / DN250 corresponds to NPS 10, commonly called a 10-inch pipe, with nominal OD 273.1 mm.

300 NB is how many inches?

300 NB / DN300 corresponds to NPS 12, commonly called a 12-inch pipe, with nominal OD 323.9 mm.

15 NB is how many inches?

15 NB / DN15 corresponds to NPS 1/2, with nominal OD 21.3 mm. Check the dimensional standard when ordering.

What is the OD of a 2-inch pipe?

NPS 2 / 50 NB has nominal OD 60.3 mm in this ASME series, rather than 50.8 mm.

What is the OD of 100 NB pipe?

100 NB / DN100 corresponds to NPS 4, with nominal OD 114.3 mm.

Does SCH 80 have a bigger outside diameter?

For the same NPS and dimensional series, the nominal OD stays the same. A thicker wall reduces the internal bore.

Is SS pipe the same weight as MS pipe?

For identical dimensions, theoretical weight changes with density. Different schedules also change wall thickness, so compare grade and dimensions together.

Does SCH 40 mean a 40 mm wall or 40 bar rating?

No. It is a schedule designation. Pressure suitability requires an engineering calculation using the material, temperature, allowances and design code.

From pipe size to a complete purchase enquiry

Consider an illustrative requirement for 50 NB SCH 40 carbon-steel seamless pipe, 10 lengths of 6 meters each.

Calculations use unrounded weights; displayed weights are rounded. ₹75/kg is an example, not a current price or offer.

Common ordering mistakes—and how to avoid them

Five details to check before ordering

1. Nominal size or actual OD? “2-inch pipe” and “50.8 mm OD tube” do not describe the same size.
2. Schedule and standard: retain the S designation for stainless schedules; confirm IS-series dimensions separately.
3. Material and manufacture: grade, product specification and seamless/welded construction belong in the enquiry.
4. Length and billing: agree actual piece length, total meters and actual-weight or nominal-weight settlement.
5. Inspection: state MTC, testing, traceability and delivery requirements before comparing offers.

Send a complete pipe enquiry

Example: “ASTM A106 Gr B seamless pipe, 50 NB / NPS 2, SCH 40, ASME B36.10, 6-meter lengths, 10 Nos, bevelled ends, MTC 3.1, delivery Mumbai.” Add inspection, IBR and project requirements where applicable.

Build a technical RFQ → · Browse pipes and tubes → · Check mating flange dimensions →

References and calculation basis

• Atlas Steels Tech Note 12, revised April 2021: nominal size, OD and schedule-wall references.
• Wheatland Tube standard pipe brochure: independent checks for common carbon-steel sizes.
• ASME B36.19 stainless pipe standard overview.

The chart is a selected reference, not a reproduction of a complete standard or proof of current-edition compliance. Check the latest applicable standard and approved project requirements before ordering.

Continue with a related guide

1D to 10D bend radius: select CLR, angle and tangent lengths →

Industrial pipes and tubes · Matching butt-weld pipe fittings · F316L stainless-steel flanges

NEW: Build a pipe connection visually →