Struggling with pipe dimension mismatches, delayed shipments, and unreliable suppliers? This authoritative guide gives purchasing managers, technical directors, and operations leaders a full steel pipe sizes in mm chart, compliance standards, and a factory-direct wholesale partner built for the US & European markets.
⚙️ Wholesale Steel Pipe & Fittings
Struggling with pipe dimension mismatches, delayed shipments, and unreliable suppliers? This authoritative guide gives purchasing managers, technical directors, and operations leaders a full steel pipe sizes in mm chart, compliance standards, and a factory-direct wholesale partner built for the US & European markets.
Every year, procurement teams lose time and money on incorrect pipe dimensions, incompatible fittings, and suppliers who can’t deliver. Here’s what we hear from buyers every day:
A 1mm ID difference can reduce flow rate by 12%, causing pressure drops and pump failures across entire plumbing networks.
Buying pipe and fittings from different sources often leads to thread compatibility issues and costly field rework. 63% of plumbing failures trace back to mismatched sizing.
Buyers waste 1–3 weeks chasing dimensional data from multiple suppliers. That’s money lost on idle crews and stalled projects.
Below is our comprehensive steel pipe sizes in mm chart based on ASME B36.10M and ASME B36.19M standards. This is the same data sheet our engineers use for every wholesale order.
| NPS | DN | Outside Dia. (mm) | Sch 5 (mm) | Sch 40 (mm) | Sch 80 (mm) | Wt Sch 40 (kg/m) |
|---|---|---|---|---|---|---|
| 1/2" | DN15 | 21.3 | 1.65 | 2.77 | 3.73 | 1.27 |
| 3/4" | DN20 | 26.7 | 1.65 | 2.87 | 3.91 | 1.69 |
| 1" | DN25 | 33.4 | 1.65 | 3.38 | 4.55 | 2.50 |
| 1-1/4" | DN32 | 42.2 | 1.65 | 3.56 | 4.85 | 3.39 |
| 1-1/2" | DN40 | 48.3 | 1.65 | 3.68 | 5.08 | 4.05 |
| 2" | DN50 | 60.3 | 1.65 | 3.91 | 5.54 | 5.44 |
| 2-1/2" | DN65 | 73.0 | 2.11 | 5.16 | 7.01 | 8.63 |
| 3" | DN80 | 88.9 | 2.11 | 5.49 | 7.62 | 11.29 |
| 4" | DN100 | 114.3 | 2.11 | 6.02 | 8.56 | 16.08 |
| 6" | DN150 | 168.3 | 2.77 | 7.11 | 10.97 | 28.26 |
| 8" | DN200 | 219.1 | 2.77 | 8.18 | 12.70 | 42.55 |
| 10" | DN250 | 273.0 | 3.40 | 9.27 | 15.09 | 60.28 |
| 12" | DN300 | 323.8 | 4.00 | 10.31 | 17.48 | 79.66 |
📐 How to read this chart: NPS = Nominal Pipe Size (inches), DN = Nominal Diameter (mm). The Outside Diameter (OD) stays constant for a given NPS regardless of schedule — only wall thickness changes. Find your pipe’s OD, then check the wall thickness for your required pressure rating.
The schedule number defines wall thickness. Higher schedules = thicker walls = higher pressure ratings. Your choice depends on operating pressure, temperature, and the medium being carried.
All steel pipes used in plumbing systems must meet strict mechanical and chemical composition requirements. At Cangzhou Weihuan Pipeline Equipment Co., Ltd., we supply the following grades with full material traceability certificates:
Seamless & welded black/hot-dipped galvanized pipe. Grade A & B available. Most common for structural and low-pressure plumbing.
Seamless carbon steel for high-temperature service. Grades A, B, C. Used in steam lines, boiler systems, and refineries.
Line pipe for oil & gas transmission. Grades B to X80. Suitable for cross-country pipelines and gathering lines.
European standard for non-alloy steel tubes suited to threading. Market-leading in the EU for plumbing and heating systems.
A steel pipe sizes in mm chart is only half the story. Every pipe needs compatible fittings. Here’s what our engineers want you to know:
An elbow changes flow direction. A 90° elbow is standard in plumbing; 45° elbows reduce turbulence where space permits. As highlighted in the Elbow Stress Indices Using Finite Element Analysis paper, a pipe bend’s cross section deforms significantly under external load — the curved geometry increases flexibility but also creates stress intensification through ovalization. This is why ASME B31 code requires stress indices when designing with elbows. Our elbows meet ASME B16.9 dimensional standards and are fully stress-relieved.
📚 Reference: academia.edu/292313
A standard tee has three openings of the same size in a “T” shape, allowing a 90-degree branch from a straight run. A reducing tee steps down to a smaller branch without needing an extra reducer. When designing, remember that tee connections produce sustained stress intensification at the discontinuity locations (per the Sustained Stress Indices at Tee Connections study). These are not “notch effects” — they must be factored into beam-type analyses per ASME B31. Our tees are forged and fully tested to handle rated pressure with zero leakage.
📚 Reference: ScienceDirect S0308016121000995
A reducer coupling connects pipes of two different sizes, with a larger female thread on one end and a smaller on the other. While elbows and tees direct flow, reducers transition diameter while maintaining pressure integrity. Our reducers are available in concentric and eccentric configurations, ensuring smooth flow transition and full pressure rating. As noted in the 2025 engineering guide on threaded pipe systems, the reducer is functionally essential where a branch line must be smaller than the main without adding an extra fitting.
📚 Reference: jianzhipipefitting.com 2025 Guide
Flanges enable easy disassembly for maintenance. Material selection is critical: the Performance Material Selection in Rigid Flange Coupling Systems paper (Cureus, 2025) provides a decision matrix evaluating mechanical properties, corrosion resistance, thermal stability, and cost. And per the Optimal Design of 6in Offshore Flange Connector study, optimized cone angles and curvature radii maximize sealing contact pressure. We offer Weld Neck, Slip-On, Blind, and Threaded flanges in ANSI, DIN, and JIS standards. Rating up to Class 2500#, available in carbon steel, stainless steel, and alloy steel.
📚 References: Cureus 2025 · DOI 10.21278/brod75207
For dynamic systems, the Simplified Nonlinear Dynamic Model for Pipe Structures with Bolted Flange Joints (Journal of Sound and Vibration, 2012) demonstrates that bolted flange joints introduce nonlinear contact stiffness. Our flange assemblies are pre-engineered with hardened bolts and precision-machined sealing surfaces to minimize joint relaxation over time — a proven factor in reducing system vibration and leak risk.
📚 Reference: DOI 10.1016/j.jsv.2011.09.002
For threaded steel pipe systems in residential and commercial plumbing, Malleable Cast Iron (MCI) fittings remain the industry standard. We produce and export a full range:
We don’t just claim quality — we prove it with certifications and third- party audits.
We don’t ask you to trust “stock photos.” Here’s what our production floor actually looks like — and a few of the global brands we supply.
* Brand logos shown are for illustrative purposes; NDA details available upon request.
As a factory-direct supplier with our own export team, we cut intermediaries. Here’s what you can expect:
Straight answers from our technical sales team.
Standard sizes range from DN15 (21.3mm OD) to DN300 (323.8mm OD) and above. For plumbing systems, DN15–DN50 (1/2" to 2") is most common, with Schedule 40 wall thickness predominating. The full chart above gives OD, wall thickness, and weight for every size.
For pipes, DN is the metric equivalent of NPS: DN = NPS × 25 (approximately). Example: 2" NPS = DN50, 4" NPS = DN100, 6" NPS = DN150. But always use a conversion chart (like ours) for exact dimensions, since the actual OD in mm doesn’t equal NPS × 25 exactly.
Schedule 80 has a thicker wall than Schedule 40 for the same NPS. Example: 2" pipe has an OD of 60.3mm. With Schedule 40, the wall is 3.91mm; with Schedule 80, the wall is 5.54mm (approx. 42% thicker). This translates to a higher pressure rating — usually around 2x the pressure rating of Schedule 40.
For standard sizes, MOQ is 1 ton or one 20ft container. For samples, we offer free samples with freight-to-door paid by the customer (or negotiable for long-term partners).
Yes. We provide custom cutting to length, threading (NPT/BSPT), beveling, and grooving per your drawings. Custom packaging and bundling options are also available.
Pricing tiers typically scale with order volume: 5–20 tons standard wholesale rate; 20–50 tons 3–5% discount; 50+ tons custom contract pricing with quarterly rate locks. Contact us for a tailor-made quote.
Every shipment includes technical documentation and our support team with English-speaking engineers available on WhatsApp and email. We also accept returns on defective products and issue credit notes within 7 days of inspection.
Real feedback from purchasing and engineering leaders across the globe.
“We switched to Weihuan for our steel pipe supply. Their dimensional accuracy is the best we’ve seen from any Chinese supplier. Our rework rate dropped by 27% because pipes and fittings actually line up now.”
“Their sample-to-bulk consistency is impressive. What we tested in sample form is exactly what arrived in the 40ft container. Lead time was 3 days earlier than promised.”
“The flange quality exceeded our expectations. Surface finish is clean, bolt holes align perfectly, and the pressure rating is accurately printed. We’ve now made them our go-to flange supplier.”
“We’ve sourced steel pipe from four countries. Weihuan’s documentation accuracy (EN 10204 3.1, heat numbers, test reports) is the most reliable. It makes our QA sign-off painless.”
With 20+ years in steel pipe manufacturing, international export, and pipeline system engineering, David has supervised over 35,000 tons of exported pipe products to the US, EU, Middle East, and Africa. He is a member of the ASME B31 piping code study group and regularly publishes technical guidance for procurement professionals.
Hundreds of buyers like you have reached out, asked hard questions, and became long-term partners. Here are snapshots of actual client conversations with our sales engineering team:
Get a factory-direct wholesale quote tailored to your project needs — with full dimensional data, material certifications, and delivery schedule in 24 hours.
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