Understanding standard stainless steel pipe sizes is essential for engineers, contractors, and buyers in industries such as construction, oil & gas, water supply, and manufacturing.
This article provides a complete guide to stainless steel pipe dimensions, wall thickness, grades, and schedules (SCH), helping you choose the correct pipe for your application in 2025.
We’ve also included an FAQ section, industry references, and real-world examples to make this a trusted, reference-level guide.
Why Standard Pipe Sizes Matter
The term “standard stainless steel pipe sizes” refers to globally accepted dimensions for outer diameter (OD), wall thickness, and internal diameter (ID).
These standardizations ensure that stainless steel pipes fit uniformly across valves, fittings, and equipment, regardless of the manufacturer or location.
In India, pipe size standards are governed by:
- ASTM (American Society for Testing and Materials)
- ASME (American Society of Mechanical Engineers)
- ANSI (American National Standards Institute)
- IS (Bureau of Indian Standards) — IS 1239, IS 3589
Understanding Stainless Steel Pipe Sizing Terminology
| Term | Meaning |
|---|---|
| NPS (Nominal Pipe Size) | The standardized system for identifying pipe size (in inches). |
| OD (Outside Diameter) | The total outer width of the pipe. |
| ID (Inside Diameter) | The usable inner width for fluid flow. |
| Schedule (SCH) | Indicates wall thickness (e.g., SCH 5, 10, 40, 80). |
| Gauge (mm) | Another method to measure pipe thickness. |
Example:
- A 2-inch SCH 40 SS Pipe means a pipe with an outer diameter of 60.3mm and a wall thickness of 3.91mm.
Common Grades of Stainless Steel Pipes
| Grade | Description | Applications |
|---|---|---|
| SS 304 / 304L | Most common, general purpose | Water lines, architecture, food processing |
| SS 316 / 316L | Marine-grade, corrosion resistant | Chemical, marine, pharma |
| SS 202 | Cost-effective alternative | Furniture, light fabrication |
| SS 310 / 310S | High temperature resistant | Furnace, heat exchangers |
| SS 409 / 430 | Ferritic, used in automotive | Exhaust systems |
Standard Stainless Steel Pipe Size Chart (in mm and inches)
1. Stainless Steel Pipes — Nominal Bore (NB) Size Chart
| Nominal Bore (NB) | Outer Diameter (mm) | Wall Thickness (mm) | Approx. Weight (kg/m) |
|---|---|---|---|
| 15 NB (½”) | 21.3 | 2.77 | 0.84 |
| 20 NB (¾”) | 26.9 | 2.87 | 1.13 |
| 25 NB (1”) | 33.7 | 3.38 | 1.68 |
| 32 NB (1¼”) | 42.4 | 3.56 | 2.27 |
| 40 NB (1½”) | 48.3 | 3.68 | 2.72 |
| 50 NB (2”) | 60.3 | 3.91 | 3.65 |
| 65 NB (2½”) | 76.1 | 5.16 | 5.90 |
| 80 NB (3”) | 88.9 | 5.49 | 7.41 |
| 100 NB (4”) | 114.3 | 6.02 | 10.56 |
| 150 NB (6”) | 168.3 | 7.11 | 19.10 |
| 200 NB (8”) | 219.1 | 8.18 | 28.28 |
| 250 NB (10”) | 273.0 | 9.27 | 40.46 |
| 300 NB (12”) | 323.9 | 10.31 | 52.79 |
(Data as per ASTM A312, Schedule 40 / ANSI B36.19M standards)
Standard Pipe Schedules (Wall Thickness)
| Schedule (SCH) | Wall Thickness (mm) | Approx. Pressure Rating (Bar) |
|---|---|---|
| SCH 5 | 1.65 – 2.11 | 20 – 25 |
| SCH 10 | 2.11 – 3.05 | 30 – 35 |
| SCH 40 | 3.68 – 6.02 | 60 – 80 |
| SCH 80 | 4.78 – 8.56 | 100 – 120 |
| SCH 160 | 6.35 – 12.7 | 150+ |
Note: Higher schedule = thicker wall = higher pressure capacity.
Choosing the Right Stainless Steel Pipe Size
Step 1: Identify Flow Requirement
Calculate internal diameter (ID) based on flow rate and velocity using standard formulas.
Step 2: Determine Pressure Rating
Choose a schedule (SCH) based on working pressure (e.g., SCH 40 for 80 Bar).
Step 3: Select Grade Based on Application
- Food & beverage → SS 304
- Marine & chemicals → SS 316
- Structural → SS 202
Step 4: Check Compatibility
Ensure fittings and flanges match the OD and schedule of the selected pipe.
Real-World Applications by Pipe Size
| Pipe Size | Common Application |
|---|---|
| ½” to 1” | Domestic plumbing, water lines |
| 1½” to 3” | Industrial and commercial piping |
| 4” to 6” | Process industries, wastewater treatment |
| 8” to 12” | Infrastructure, oil & gas pipelines |
Price Range of Stainless Steel Pipes (2025, India)
| Grade | Type | Price (₹/kg) |
|---|---|---|
| SS 304 | Seamless | ₹280 – ₹350 |
| SS 316 | Seamless | ₹340 – ₹420 |
| SS 202 | Welded | ₹180 – ₹250 |
| SS 310 | Seamless | ₹480 – ₹600 |
(Source: IndustrialInfo Price Index, Oct 2025)
Outbound link suggestion: Indian Stainless Steel Development Association (ISSDA)
How to Read a Stainless Steel Pipe Marking
Example marking on pipe:
TATA SS 304 ASTM A312 TP304 SCH40 3” x 6m HEAT NO: 32145
Meaning:
- TATA: Manufacturer
- SS 304: Material grade
- ASTM A312: Standard specification
- SCH40: Wall thickness schedule
- 3” x 6m: Nominal bore and length
- Heat No: Batch identification for traceability
Industry Insight (Expert Quote)
“Choosing the correct stainless steel pipe size is about more than diameter; it’s about application safety, flow rate, and material strength. Standardization ensures that every project meets international quality benchmarks.”
— Dr. S. Iyer, Senior Metallurgical Engineer, Indian Institute of Metals
Frequently Asked Questions (FAQ)
Q1: What is the most common stainless steel pipe size?
½” to 4” are most common in domestic and industrial applications.
Q2: What does Schedule 40 mean in pipes?
It defines wall thickness — Schedule 40 is standard strength for most industrial systems.
Q3: How to calculate stainless steel pipe weight?
Weight = 0.02466 × (OD – WT) × WT × Length (in meters).
Q4: Which grade of SS pipe is best for corrosion resistance?
SS 316L performs best in marine and chemical environments.
Q5: What standards define SS pipe sizes?
ASTM A312, ANSI B36.19M, and IS 1239.
Conclusion
The standard stainless steel pipe size chart simplifies the process of selecting the right pipe for industrial, commercial, or domestic use.
Whether you’re designing pipelines for oil & gas, water treatment, or construction, following ASTM and IS standards ensures safety, compatibility, and long-lasting performance.
For 2025, industries are increasingly shifting to SS 316 and SS 304L pipes, balancing corrosion resistance with strength and cost efficiency.