ERW Pipe Sizes & Weight Chart — NB to OD/Schedule reference

How do NB, OD, and schedule relate in ERW pipe sizing?

NB is a nominal trade size; OD is the actual outside diameter used for fitment. Schedule or class changes wall thickness while OD usually stays fixed. Therefore two pipes with the same NB can have different bore, weight, and pressure capacity.

A 50 NB pipe is not 50 mm OD. Nominal bore is a naming convention, while OD follows a fixed pipe series. As wall thickness increases, the inside diameter decreases and the weight per metre rises. This is why fittings match OD, while hydraulic calculations need inside diameter and roughness.

Indian ERW buying often uses IS 1239 light/medium/heavy classes for smaller water and gas lines. International or project drawings may use schedule terminology such as Sch 40 or Sch 80. Both methods describe wall thickness, but they are not automatically interchangeable. Always confirm the actual wall in millimetres when converting between class and schedule.

For a standards basis, cite IS 1239 Part 1 for small ERW tubes and IS 3589 for larger water-transmission sizes. For export or mixed welded/seamless procurement, ASTM A53 terminology may appear; translate it back to OD and wall before comparing quotes.

What this ERW size chart is, and what it is not

This page converts NB to OD, wall, class or schedule, and theoretical kg/m for ERW buying. It is not a pressure-rating table, a stock list, or a substitute for the mill dimensional table named on the PO.

NB is a trade name. OD is the number that fittings, clamps, and sleeves see. Wall is the number that mass, bore, and thread engagement follow. IS class and ASME schedule are two wall languages. They share some sizes and diverge on others. 150 NB on the IS 1239 class chart uses OD 165.1 mm. ASME 6 inch uses OD 168.3 mm. Those are different tubes.

The chart does not pick class for you. A PWD water line, a fire header, and a handrail can share NB and still need different walls. Hydraulic and printing-cylinder work need bore and tolerance this commodity chart does not give. IBR steam parts need seamless boiler dimensions, not an IS 1239 row.

Use the class thickness chart for Light/Medium/Heavy millimetres and the pipe schedule chart for Sch 40 and Sch 80. Keep both open when a mixed BOQ uses class on one line and schedule on the next.

Who in Kanpur should use this size and weight chart

Kanpur contractors, PWD and JJM buyers, fabricators, and storekeepers should use it to check quotations and weighbridge slips. Designers still own flow, pressure, and corrosion allowance. Do not use it to swap class or schedule without drawing approval.

A Kanpur store that issues “50 NB pipe” without class will mix Light and Medium on the same rack. The chart makes that error visible in kilograms. Pump-house work in Panki, fabrication in Dada Nagar, and tannery utilities in Jajmau all buy on NB. The receiving clerk still needs OD, wall, and kg/m on the GRN.

Do not use the chart to justify a cheaper class on a fire line, a buried main, or a threaded high-abuse run. Do not use it to order hydraulic barrel stock or printing-cylinder blanks. Those jobs live on precision-tube pages. Sugar-mill steam parts live on seamless boiler pages.

Link the local buy to steel pipes in Kanpur, MS ERW in Kanpur, and the Kanpur steel market guide. Rates stay ex-warehouse Kanpur with GST extra at the legally applicable GST rate stated on the current quotation.

How is ERW pipe weight per metre calculated for buying?

The standard steel-pipe formula is weight kg/m = 0.02466 × wall × (OD − wall), using millimetres. It estimates theoretical mass before coating, threading, and tolerance. Purchase managers should compare quoted bundles against theoretical weight to catch an underspecified wall before the PO is released.

The formula is useful because steel pipe is usually priced by kilogram or metric tonne, while sites consume lengths. If a supplier quotes very low per length, calculate whether the wall class is lighter than requested. Small wall differences across hundreds of metres can move tonnage and pressure margin materially.

Theoretical weight is not the same as exact dispatch weight. Mill tolerances, zinc coating, couplings, moisture, and cutting practice change the weighbridge number. Still, theoretical mass is the cleanest apples-to-apples benchmark at RFQ stage. Ask the supplier to show size, wall, length, and tonnage on the quotation rather than hiding weight inside a lump-sum line.

Use the site calculator for quick estimates, then lock the RFQ with OD and wall. If the pipe must fit clamps, sleeves, pump housings, or prefabricated supports, OD tolerance matters as much as weight.

IS 1239 size, wall, and kg/m chart for common NB

The table reuses the site class chart and weight table. 25 NB medium is 33.7 mm OD, 3.2 mm wall, 2.41 kg/m. 50 NB medium is 60.3 mm OD, 3.6 mm wall, 5.03 kg/m. 100 NB medium is 114.3 mm OD, 4.5 mm wall, 12.18 kg/m.

Units are millimetres and kilograms. Mass is theoretical plain-end MS, not galvanized mass. As-of date is 2026-05-06, matching the class chart and generated weight file. Indicative MS ERW bands on the price list last edited 24 May 2026 are ₹47-70 per kg ex-warehouse Kanpur. That dated list shows GST 18% extra as a budgeting example, not a locked current tax rate.

150 NB on this IS chart is 165.1 mm OD. IS 3589 water mains start at 168.3 mm OD. Do not treat those rows as the same pipe. Zinc coating adds mass, but there is no defensible universal percentage uplift: calculate from the specified coating and tube geometry or use the certified dispatch mass.

Important source conflict: the linked IS 1239 standard guide currently shows 2.90 mm for 50 NB Medium, while the class thickness chart and pipe-weight table used here show 3.6 mm and 5.03 kg/m. The worked figures on this page use 3.6 mm. Do not release a PO from either website value alone; reconcile the purchased BIS edition, tender, mill table, and offered MTC first.

When should a buyer choose IS class instead of Schedule 40 or 80?

Use IS light/medium/heavy class when the project drawing or Indian water/gas specification cites IS 1239. Use Schedule 40 or 80 when the drawing follows ASME/ASTM pipe schedules. Never substitute by name alone; compare actual OD and wall.

IS class language is familiar in plumbing, fabrication, and utility procurement. Schedule language appears in process piping, EPC drawings, and export-linked projects. A supplier may have both in stock, but a name match does not guarantee dimensional equivalence. For example, an IS medium pipe near a nominal size may not equal Sch 40 exactly.

Where pressure, threading, or welding qualification matters, ask the engineer to approve the wall in millimetres. Procurement should not “upgrade” or “downgrade” schedules without design approval because bore, flow, thread engagement, and support load change. Schedule 80 increases wall and reduces inside bore; that can increase pump head loss.

For mixed networks, create a schedule in the bill of quantities: each line should show service, NB, OD, wall, class or schedule, grade, finish, and quantity. That prevents site teams from using a water-line class pipe in a process line simply because the nominal size matches.

What size and weight checks should be done before accepting ERW pipe?

Check OD, wall, length, straightness, end condition, coating, heat number, MTC, and bundle weight. Compare dispatch weight with theoretical weight and tolerance. Hold visibly oval, dented, short, mixed-class, or undocumented pipe before cutting or installation.

Incoming inspection should sample each size and class. Measure wall with a calibrated gauge at several points because weld-area thickness and ovality can affect fitment. Count lengths, verify bundle tags, and match MTC numbers. If galvanized, inspect white rust, bare spots, and threaded-end condition.

Bundle weight is a useful fraud and error check. A truck delivering 100 lengths of “medium” pipe that weighs like light class needs explanation before unloading acceptance. Some variation is normal, but a systematic shortfall suggests wrong class, wrong wall, or mixed stock.

Keep inspection evidence before fabrication. Once pipe is cut, threaded, painted, or welded, suppliers can reasonably argue that the material was accepted. A five-minute weight and wall check is cheaper than discovering the wrong class after installation.

How Kanpur buyers should write size and mass on an RFQ

State NB, OD if fitment matters, wall in millimetres, class or schedule, grade, length, quantity in metres and MT, finish, ends, MTC, and delivery basis. Do not order by NB alone.

A Kanpur RFQ that says only “50 NB ERW, 100 lengths” invites Light class against a Medium BOQ. Write IS 1239 Medium, OD 60.3 mm, the reconciled wall in millimetres, length, black or GI, and plain or T&C. Do not add YST 210/240/310 as an IS 1239 grade menu; add a material designation only when a separate project specification requires it. If the drawing uses Sch 40, write Sch 40 and its millimetre wall, not “medium equivalent”.

Ask for theoretical mass on the quotation and actual weighbridge mass on dispatch. Confirm cut-length availability, offered mill length, MTC, and any TPI scope for the specific stock and vehicle before allocation; do not assume one document or service promise applies to every lot.

Commercials stay split: ex-warehouse Kanpur, GST extra at the legally applicable GST rate stated on the current quotation, freight by destination PIN. Send the line through the RFQ form with the calculator print-out attached if the quantity is large.

• Identity: standard, class or schedule, plus the exact material grade only when the governing project specification names one.
• Size: NB, OD in mm, wall in mm, length, end finish, piece count and MT.
• Mass: theoretical kg/m shown on the quote; weighbridge kg on the GRN.
• Documents: inspection-document type, heat marking, test evidence, and TPI scope as named by the PO.
• Delivery: ex-warehouse Kanpur, GST at the legally applicable GST rate stated on the current quotation, freight, destination PIN.

Worked mass check for 100 lengths of 50 NB medium

50 NB medium is 5.03 kg/m and 30.2 kg per 6 m on the site table. One hundred 6 m lengths are 3.02 MT theoretical. A quote near 2.46 MT for the same piece count is Light class mass, not a discount.

Formula: (60.3 − 3.6) × 3.6 × 0.02466 = 5.03 kg/m. Table mass per 6 m is 30.2 kg. 100 × 30.2 kg = 3,020 kg = 3.02 MT. Light class at the same NB is 4.10 kg/m and 24.6 kg per 6 m, or 2.46 MT for 100 lengths. Heavy class is 6.19 kg/m and 37.1 kg per 6 m, or 3.71 MT.

The 50 NB medium band on the dated MS ERW price list is ₹53-60 per kg. 3.02 MT on that band is about ₹1.60 lakh to ₹1.81 lakh before tax and freight. Apply only the legally applicable tax stated on the current quotation. Freight from Kanpur must be quoted separately for the named destination and load.

If the truck weighs 2.5 MT for a Medium PO, stop unloading. Recheck wall with a gauge. The weight calculator repeats the same formula for other sizes.

Dispatch from Kanpur when size and mass are locked

Once NB, wall, and theoretical MT are on the PO, obtain a Kanpur dispatch plan tied to confirmed stock, document availability, vehicle capacity, destination access, and carrier transit. GST is extra at the legally applicable GST rate stated on the current quotation on an ex-warehouse Kanpur basis.

For Kanpur, Lucknow, Prayagraj, Varanasi, or another destination, confirm loading and transit against current stock and carrier availability. Bundle tags must show size and class if multiple NB sizes share a proposed load.

A 3.02 MT 50 NB Medium lot may require a part-load or consolidation depending on the vehicle offered. Confirm whether mixed loads are available and require the agreed weighbridge slip, GST invoice, e-way bill, MTC, and packing list before dispatch.

Use steel pipes Lucknow or the other city pages for transit notes. Do not promise a site time from this chart alone.

Key points for ERW size and weight buying

These five checks close the size decision. They rest on the table and formula above.

• Convert NB to OD, then lock wall in millimetres by class or schedule.
• Compute kg/m with (OD − t) × t × 0.02466 before comparing length rates.
• 50 NB medium is 5.03 kg/m and 30.2 kg per 6 m on the site table.
• 150 NB IS 1239 uses 165.1 mm OD; ASME 6 inch uses 168.3 mm.
• Quote ex-warehouse Kanpur with GST extra at the legally applicable GST rate stated on the current quotation and freight separate.