Steel Pipe Dimensions & Sizes — Complete Guide to Schedule 40, 80 Pipe
Steel Pipe Dimensions Size is a critical specification in both engineering design and material procurement because it determines system compatibility, flow capacity, pressure performance, and installation requirements. A clear understanding of steel pipe size terminology—including Nominal Pipe Size (NPS), Nominal Diameter (DN), outside diameter, wall thickness, and pipe schedule—is essential for selecting and ordering the correct product.This article will let you fully understand the size parameters of steel pipe, so that you can solve 90% of the problems in design, installation and purchase.
Quick Check Your Size In Table
Steel Pipe Dimensions Chart
Steel Pipe Dimensions Chart — Nominal Wall Thickness Schedule (mm)
| NPS | DN | OD | 5s | 10s | 10 | 20 | 30 | 40s | STD | 40 | 60 | 80s | XS | 80 | 100 | 120 | 140 | 160 | XXS |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/8 | 6 | 10.3 | — | 1.24 | — | — | — | 1.73 | 1.73 | 1.73 | — | 2.41 | 2.41 | 2.41 | — | — | — | — | — |
| 1/4 | 8 | 13.7 | — | 1.65 | — | — | — | 2.24 | 2.24 | 2.24 | — | 3.02 | 3.02 | 3.02 | — | — | — | — | — |
| 3/8 | 10 | 17.1 | — | 1.65 | — | — | — | 2.31 | 2.31 | 2.31 | — | 3.20 | 3.20 | 3.20 | — | — | — | — | — |
| 1/2 | 15 | 21.3 | 1.65 | 2.11 | — | — | — | 2.77 | 2.77 | 2.77 | — | 3.73 | 3.73 | 3.73 | — | — | — | 4.78 | 7.47 |
| 3/4 | 20 | 26.7 | 1.65 | 2.11 | — | — | — | 2.87 | 2.87 | 2.87 | — | 3.91 | 3.91 | 3.91 | — | — | — | 5.56 | 7.82 |
| 1 | 25 | 33.4 | 1.65 | 2.77 | — | — | — | 3.38 | 3.38 | 3.38 | — | 4.55 | 4.55 | 4.55 | — | — | — | 6.35 | 9.09 |
| 1 1/4 | 32 | 42.2 | 1.65 | 2.77 | — | — | — | 3.56 | 3.56 | 3.56 | — | 4.85 | 4.85 | 4.85 | — | — | — | 6.35 | 9.70 |
| 1 1/2 | 40 | 48.3 | 1.65 | 2.77 | — | — | — | 3.68 | 3.91 | 3.91 | — | 5.08 | 5.08 | 5.08 | — | — | — | 7.14 | 10.15 |
| 2 | 50 | 60.3 | 1.65 | 2.77 | — | — | — | 3.91 | 3.91 | 3.91 | — | 5.54 | 5.54 | 5.54 | — | — | — | 8.74 | 11.07 |
| 2 1/2 | 65 | 73 | 2.11 | 3.05 | — | — | — | 5.16 | 5.16 | 5.16 | — | 7.01 | 7.01 | 7.01 | — | — | — | 9.53 | 14.02 |
| 3 | 80 | 88.9 | 2.11 | 3.05 | — | — | — | 5.49 | 5.49 | 5.49 | — | 7.62 | 7.62 | 7.62 | — | — | — | 11.13 | 15.24 |
| 3 1/2 | 90 | 101.6 | 2.11 | 3.05 | — | — | — | 5.74 | 5.74 | 5.74 | — | 8.08 | 8.08 | 8.08 | — | — | — | — | — |
| 4 | 100 | 114.3 | 2.11 | 3.05 | — | — | — | 6.02 | 6.02 | 6.02 | — | 8.56 | 8.56 | 8.56 | 11.13 | — | — | 13.49 | 17.12 |
| 5 | 125 | 141.3 | 2.77 | 3.40 | — | — | — | 6.55 | 6.55 | 6.55 | — | 9.53 | 9.53 | 9.53 | 12.70 | — | — | 15.88 | 19.05 |
| 6 | 150 | 168.3 | 2.77 | 3.40 | — | — | — | 7.11 | 7.11 | 7.11 | — | 10.97 | 10.97 | 10.97 | 14.27 | — | — | 18.26 | 21.95 |
| 8 | 200 | 219.1 | 2.77 | 3.76 | 6.35 | 7.04 | 8.18 | 8.18 | 8.18 | 8.18 | 10.31 | 12.70 | 12.70 | 15.09 | 15.09 | 18.26 | 20.62 | 23.01 | 22.23 |
| 10 | 250 | 273.1 | 3.40 | 4.19 | 6.35 | 7.80 | 9.27 | 9.27 | 9.27 | 9.27 | 12.70 | 12.70 | 12.70 | 15.09 | 18.26 | 21.44 | 25.40 | 28.58 | 25.40 |
| 12 | 300 | 323.9 | 3.96 | 4.57 | 6.35 | 8.38 | 9.53 | 9.53 | 9.53 | 10.31 | 14.27 | 12.70 | 12.70 | 17.48 | 21.44 | 25.40 | 28.58 | 33.32 | 25.40 |
| 14 | 350 | 355.6 | 3.96 | 4.78 | 6.35 | 7.92 | 9.53 | — | 9.53 | 11.13 | 15.09 | — | 12.70 | 19.05 | 23.83 | 27.79 | 27.79 | 31.75 | 35.71 |
| 16 | 400 | 406.4 | 4.19 | 4.78 | 6.35 | 7.92 | 9.53 | — | 9.53 | 12.70 | 16.66 | — | 12.70 | 21.44 | 25.19 | 26.96 | 30.55 | 36.53 | 40.49 |
| 18 | 450 | 457.2 | 4.19 | 4.78 | 6.35 | 7.92 | 11.13 | — | 9.53 | 14.27 | 19.05 | — | 12.70 | 23.83 | 29.36 | 24.98 | 38.57 | 39.67 | 45.24 |
| 20 | 500 | 508 | 4.78 | 5.54 | 6.35 | 9.53 | 12.70 | — | 9.53 | 15.09 | 20.62 | — | 12.70 | 26.19 | 32.54 | 38.10 | 40.10 | 44.45 | 50.01 |
| 22 | 550 | 559 | 4.78 | 5.54 | 6.35 | 9.53 | 12.70 | — | 9.53 | — | 22.23 | — | 12.70 | 28.58 | 34.93 | — | 41.58 | 47.63 | 53.98 |
| 24 | 600 | 610 | 5.54 | 6.35 | 6.35 | 9.53 | 14.27 | — | 9.53 | 17.48 | 24.61 | — | 12.70 | 30.96 | 38.89 | 46.02 | 56.67 | 52.37 | 59.54 |
| 26 | 660 | 660 | — | — | 7.92 | 12.70 | — | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
| 28 | 700 | 711 | — | — | 7.92 | 12.70 | 15.88 | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
| 30 | 750 | 762 | 6.35 | 7.92 | 7.92 | 12.70 | 15.88 | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
| 32 | 800 | 813 | — | — | 7.92 | 12.70 | 15.88 | — | 9.53 | 17.48 | — | — | 12.70 | — | — | — | — | — | — |
| 34 | 850 | 884 | — | — | 7.92 | 12.70 | 15.88 | — | 9.53 | 17.48 | — | — | 12.70 | — | — | — | — | — | — |
| 36 | 900 | 914 | — | — | 7.92 | 12.70 | 15.88 | — | 9.53 | 19.05 | — | — | 12.70 | — | — | — | — | — | — |
| 38 | 950 | 965 | — | — | — | — | — | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
| 40 | 1000 | 1016 | — | — | — | — | — | — | 9.53 | — | 12.70 | — | — | — | — | — | — | — | — |
| 42 | 1050 | 1067 | — | — | — | 12.70 | 15.88 | — | 9.53 | 19.05 | — | — | 12.70 | — | — | — | — | — | — |
| 44 | 1100 | 1118 | — | — | — | — | — | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
| 46 | 1150 | 1168 | — | — | — | — | — | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
| 48 | 1200 | 1219 | — | — | — | — | — | — | 9.53 | — | — | — | 12.70 | — | — | — | — | — | — |
Pipe Dimensions & Weight Calculator
Calculated Specifications
Wall Thickness
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mm
Inside Diameter
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mm
Weight
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kg/m
Weight
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lb/ft
NPS
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DN
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OD
—
Schedule
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All available schedules for this size
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Understanding Steel Pipe Dimensions — 3 Key Elements
Every steel pipe — from small-bore plumbing to large-diameter OCTG casing — is defined by three fundamental measurements. These steel pipe dimensions determine the pipe's weight, pressure capacity, and cost. Understanding them is the first step to reading any specification sheet or placing an accurate order.
1
Outer Diameter (OD)
The outside measurement of the pipe cross-section
2
Wall Thickness (WT)
How thick the pipe wall is — controls strength & weight
3
Pipe Length
Overall length per joint — affects shipping & handling
Outer Diameter (OD) and Nominal Pipe Size (NPS)
The outer diameter is the actual outside measurement of the pipe in inches or millimeters. It is the most fundamental steel pipe measurement because it determines which fittings, couplings, and wellbore configurations the pipe is compatible with.
In North America, metal pipe diameters are referenced using the NPS (Nominal Pipe Size) system. Internationally, the equivalent is DN (Diameter Nominal), expressed in millimeters.
Key rule: For NPS ≤ 12, the nominal size does not equal the actual OD. For example, NPS 4 has an actual OD of 4.500″ — not 4.000″. Only at NPS 14 and above does the nominal size match the actual OD in inches.
| NPS | DN (mm) | Actual OD (in) | Actual OD (mm) | NPS = OD? |
|---|---|---|---|---|
| 1 | 25 | 1.315 | 33.4 | No |
| 2 | 50 | 2.375 | 60.3 | No |
| 4 | 100 | 4.500 | 114.3 | No |
| 8 | 200 | 8.625 | 219.1 | No |
| 12 | 300 | 12.750 | 323.9 | No |
| 14 | 350 | 14.000 | 355.6 | Yes |
| 20 | 500 | 20.000 | 508.0 | Yes |
DN-to-NPS conversion: For DN ≥ 100, the approximate rule is DN = 25 × NPS. For example, NPS 4 = DN 100, NPS 8 = DN 200. Below DN 100, the relationship is non-linear and must be looked up from a reference table.
Wall Thickness and Pipe Schedule Explained
Wall thickness determines how much pressure a pipe can withstand and how much it weighs per meter or foot. In standardized piping, wall thickness is expressed through pipe schedules (SCH) — a numbering system where higher numbers mean thicker walls and higher pressure ratings.
For the same OD, a SCH 40 pipe thickness is moderate and suits most general-purpose applications, while a SCH 160 pipe thickness is much heavier and designed for high-pressure service. The most commonly referenced schedules are SCH 10, 20, 40, 80, 120, and 160.
Calculated Schedule Number
—
Where P is the working pressure, and [σ]t is the allowable stress at the operating temperature. This formula shows that the schedule number is a function of pressure and material strength — not a fixed wall thickness value.
| NPS | OD (in) | SCH 40 WT (in) | SCH 80 WT (in) | SCH 160 WT (in) |
|---|---|---|---|---|
| 2 | 2.375 | 0.154 | 0.218 | 0.344 |
| 4 | 4.500 | 0.237 | 0.337 | 0.531 |
| 6 | 6.625 | 0.280 | 0.432 | 0.719 |
| 8 | 8.625 | 0.322 | 0.500 | 0.906 |
| 12 | 12.750 | 0.406 | 0.688 | 1.312 |
Important: The same schedule number produces different actual wall thicknesses at different OD sizes. For example, SCH 40 on a 2″ pipe is 0.154″, but SCH 40 on a 12″ pipe is 0.406″. Always verify the actual WT for the specific OD — never assume a schedule implies a fixed thickness.
How to Describe Steel Pipe Dimensions and Size Correctly
A complete steel pipe specification always includes three elements: outside diameter, wall thickness (or schedule), and length. Omitting any one of them can lead to ordering errors, material mismatches, or project delays.
How to describe steel pipe dimensions correctly: The standard format is OD × WT × Length. For example, 219.1 mm × 8.18 mm × 6000 mm, which equals NPS 8, SCH 40 (STD). Three elements are required: (1) Outside Diameter (OD), (2) Wall Thickness (WT) or Schedule (SCH), and (3) Overall pipe length in mm or feet. The unit weight formula is W (kg/m) = 0.02466 × (OD − WT) × WT, where OD and WT are in millimeters. The inside diameter (ID) is calculated as OD minus two times WT. In this example, ID = 219.1 − 2 × 8.18 = 202.7 mm.
OD — Outside Diameter
OD is the actual outside diameter of the pipe. It may be written in millimeters, inches, or referenced by a nominal pipe size.
Inches
1 inch = 1"
Metric
1" = 25.4 mm
Symbol
Ø219.1 mm / OD 219.1 mm
Nominal
NPS 8 / 8" NPS / DN200
Important: NPS and DN are nominal size designations,
not always the actual outside diameter. For example,
NPS 8 / DN200 has an actual OD of 219.1 mm (8.625").
WT — Wall Thickness
WT is the thickness of the pipe wall. It can be given as an exact dimension or represented by a pipe schedule.
Metric
8.18 mm / WT 8.18 mm
Inches
0.322" / 0.322 inch
Schedule
SCH 40 / Sch. 40 / Schedule 40
Classes
STD / XS / XXS
Remember: SCH 40 does not mean the same wall thickness
for every pipe size. Always check the NPS together with the schedule.
For NPS 8 SCH 40, WT = 8.18 mm (0.322").
Length — Pipe Length
Length is measured from one pipe end to the other and may be stated in metric, imperial, fixed, or random-length formats.
Metric
6 m = 6000 mm
Feet
20 ft = 20' ≈ 6.096 m
Fixed
L = 6000 mm / 6 m fixed length
Random
SRL / DRL / Random Length
OCTG
R1 / R2 / R3
Do not confuse the symbols:
1" = 1 inch = 25.4 mm, while
1' = 1 foot = 12" = 304.8 mm.
For pipe orders, always confirm whether the required length is fixed,
random, or a specified range.
Frequently Asked Questions (FAQs)
Schedule 80 is thicker than Schedule 40 at the same nominal pipe size. The thickness difference varies by pipe size; Schedule 80 is not twice as thick as Schedule 40.
| NPS | ½″ | ¾″ | 1″ | 1½″ | 2″ | 3″ | 4″ |
| Sch 40 | 2.77 | 2.87 | 3.38 | 3.68 | 3.91 | 5.49 | 6.02 |
| Sch 80 | 3.73 | 3.91 | 4.55 | 5.08 | 5.54 | 7.62 | 8.56 |
Use Schedule 40 when it meets the system’s design requirements, and select Schedule 80 when calculations or project specifications require a thicker wall, such as for higher pressure or additional corrosion allowance.
Schedule 40 is thicker than Schedule 10 at the same nominal pipe size.
There is no universal maximum steel pipe size; availability depends on the manufacturer, production process, and project requirements. For example, Balingsteel manufactures engineered steel water pipe in diameters from 12 to 156 inches—approximately 305 to 3,962 mm—and offers larger sizes on request. This represents one manufacturer’s capabilities, not an industry-wide limit.
Steel pipe is designated by nominal pipe size, rather than its exact ID or OD. For NPS 12 and smaller, the nominal size differs from the actual OD; for NPS 14 and larger, the NPS number equals the OD in inches.
Steel pipe is commonly specified by Nominal Pipe Size (NPS) and wall thickness schedule. Common sizes include NPS ½, ¾, 1, 1¼, 1½, 2, 2½, 3, 4, 6, 8, 10, and 12, with larger sizes also available. Dimensions are standardized by ASME B36.10 for wrought steel pipe and ASME B36.19 for stainless steel pipe. Available size and schedule combinations vary by manufacturer.
Reference Sources
Organization: American Society of Mechanical Engineers (ASME)
Type: Official Standard / Steel Pipe Dimensional Reference
Publication Year: 2022
Citation Token: (ASME, B36.10-2022)
Nofollow Link: ASME B36.10 — Welded and Seamless Wrought Steel Pipe
Organization: Wheatland Tube / Zekelman Industries
Type: Manufacturer Technical Brochure / Pipe Dimensions and Tolerances
Publication Year: Not specified
Citation Token: (Wheatland Tube, Standard Pipe Brochure)
Nofollow Link: Wheatland Tube — Standard Pipe Brochure (PDF)
Organization: Gems Sensors & Controls
Type: Manufacturer Technical Article / NPS, DN, OD, and Pipe Schedule Reference
Publication Year: 2026 (January 27)
Citation Token: (Gems Sensors & Controls, 2026)
Nofollow Link: Gems Sensors — Understanding Pipe Size Standards for Clamp-On Flow Measurement
Organization: Northwest Pipe Company
Type: Manufacturer Product Page / Steel Pipe Diameter Range and Custom Manufacturing Capabilities
Publication Year: Not specified
Citation Token: (Northwest Pipe Company, Engineered Steel Water Pipe)
Nofollow Link: Northwest Pipe Company — Engineered Steel Water Pipe
