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
—
mm
Inside Diameter
—
mm
Weight
—
kg/m
Weight
—
lb/ft
NPS
—
DN
—
OD
—
Schedule
—
All available schedules for this size
Request a Quote
Pre-filled with your selected specs
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.
