steel pipe sizes in mm chart for plumbing systems | Wholesale

⚙️ Wholesale Steel Pipe & Fittings

Steel Pipe Sizes in mm Chart for Plumbing Systems: Complete Dimensional Reference & Wholesale Sourcing Guide 2026

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.

📋 Table of Contents

⚠️ Why Pipe Sizing Mistakes Cost Your Business Thousands

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:

📊 Steel Pipe Sizes in mm Chart: The Master Dimensional Reference for Plumbing Systems

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.

📐 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.

🔬 Schedule & Wall Thickness: What Determines Pipe Strength?

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.

🧪 Material Grades & Compliance Standards

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:

🔩 Matching Fittings: Elbows, Tees, Reducers & Flanges

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:

🔗 Malleable Cast Iron (MCI) Fittings: The Versatile Workhorse

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:

🏅 Quality Certifications & Factory Integrity

We don’t just claim quality — we prove it with certifications and third- party audits.

ISO 9001

CE Marking

UL Listed

GS Tested

ANSI

• ✔️ Hydrostatic Testing: 100% of pipes pressure-tested at 1.5x rated pressure

• ✔️ Dimensional Inspection: Laser-based OD/wall thickness verification on every batch

• ✔️ Chemical Analysis: Spectrometer verification of C, Mn, P, S, Si content

• ✔️ Third-Party Inspection: SGS, BV, TÜV inspection welcome at customer’s request

🏭 Inside Our Factory & Global Client Base

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.

🌍 Trusted by Industry Leaders Across 20+ Countries

* Brand logos shown are for illustrative purposes; NDA details available upon request.

💰 Wholesale Pricing & Logistics: How We Save You 20–37%

As a factory-direct supplier with our own export team, we cut intermediaries. Here’s what you can expect:

❓ Frequently Asked Questions

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.

⭐ What Our Clients Say About Us

Real feedback from purchasing and engineering leaders across the globe.

John Miller

Purchasing Manager, US Plumbing Distributor

“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.”

Marco van der Berg

Operations Director, Dutch Industrial Contractor

“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.”

Sarah Thompson

Supply Chain Manager, UK MRO Supplier

“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.”

Ahmed Al-Rashid

Procurement Head, Middle East EPC Firm

“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.”

💬 Real Conversations, Real Proof

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:

🚀 Ready to Source Steel Pipe That Meets Your Specs & Budget?

Get a factory-direct wholesale quote tailored to your project needs — with full dimensional data, material certifications, and delivery schedule in 24 hours.