In the piping industry, we are no strangers to “Schedule Dimensions,” a term frequently used in the production and procurement of pipes. So, what exactly do “Schedule Dimensions” mean, and where are they typically used? How should we apply them? In the following sections, we will explore “Schedule Dimensions” from various angles—including their definition, dimensions, and applications—to provide you with a clearer understanding.
Definition of Schedule Dimensions
“Schedule Dimensions” is a common term in the piping industry that refers to the wall thickness grade of a pipe; it is often abbreviated as “Sch.” “Schedule” does not denote a specific dimension on its own, but rather is used within a comprehensive pipe description system, that includes the outside diameter (NPS), wall thickness (SCH), inside diameter, and corresponding steel grade.
“Schedule” does not represent an actual numerical value, but rather a numerical designation for wall thickness grades. For example: Schedule 10 represents thin wall thickness; Schedule 40 represents standard wall thickness; Schedule XXS represents extra-thick wall. Furthermore, within the same Schedule, different NPS sizes correspond to different wall thickness values. For instance, for Schedule 40 pipe, an NPS of 2” has a wall thickness of 3.91 mm, while an NPS of 6” has a wall thickness of 7.11 mm. Therefore, SCH is a grade code, not a fixed wall thickness.
The Schedule System
LoSchedule Dimensions are primarily used in the American standard pipe sizing system (ASME/ANSI). When the number following “Schedule” is not preceded by an “s,” it refers to carbon steel; when preceded by an “s,” it refers to the stainless steel sizing system. The core standards include: ASME B36.10M and ASME B36.19M.
Although commonly used in the U.S., these standards also serve as a reference in global procurement and pipeline production and design. All engineers are familiar with the “SCH 40” pipe specification, which helps standardize pipeline production.rem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.
Schedule Dimensions Charts
Carbon Steel SCH Size Comparison Chart
| NPS | OD | SCH 10 | SCH 20 | SCH 30 | SCH 40 | SCH 60 | SCH 80 | SCH 100 | SCH 120 | SCH 140 | SCH 160 |
| 1/8″ | 10.3 | 1.73 | — | — | 2.41 | — | 3.2 | — | — | — | — |
| 1/4″ | 13.7 | 2.24 | — | — | 3.02 | — | 3.81 | — | — | — | — |
| 3/8″ | 17.1 | 2.31 | — | — | 3.2 | — | 4 | — | — | — | — |
| 1/2″ | 21.3 | 2.11 | — | — | 2.77 | — | 3.73 | — | — | — | 4.78 |
| 3/4″ | 26.7 | 2.11 | — | — | 2.87 | — | 3.91 | — | — | — | 5.56 |
| 1″ | 33.4 | 2.77 | — | — | 3.38 | — | 4.55 | — | — | — | 6.35 |
| 1-1/4″ | 42.2 | 2.77 | — | — | 3.56 | — | 4.85 | — | — | — | 6.35 |
| 1-1/2″ | 48.3 | 2.77 | — | — | 3.68 | — | 5.08 | — | — | — | 7.14 |
| 2″ | 60.3 | 2.77 | — | — | 3.91 | — | 5.54 | 8.74 | — | — | 8.74 |
| 2-1/2″ | 73 | 3.05 | — | — | 5.16 | — | 7.01 | — | — | — | 9.53 |
| 3″ | 88.9 | 3.05 | — | — | 5.49 | — | 7.62 | 11.13 | — | — | 11.13 |
| 3-1/2″ | 101.6 | 3.05 | — | — | 5.74 | — | 8.08 | — | — | — | — |
| 4″ | 114.3 | 3.05 | — | — | 6.02 | — | 8.56 | 13.49 | — | — | 13.49 |
| 5″ | 141.3 | 3.4 | — | — | 6.55 | — | 9.53 | — | — | — | 15.88 |
| 6″ | 168.3 | 3.4 | — | — | 7.11 | 10.97 | 10.97 | 14.27 | 18.26 | — | 18.26 |
| 8″ | 219.1 | 3.76 | 6.35 | 7.04 | 8.18 | 10.31 | 12.7 | 15.09 | 18.26 | 20.62 | 23.01 |
| 10″ | 273 | 4.19 | 6.35 | 7.8 | 9.27 | 12.7 | 15.09 | 18.26 | 21.44 | 25.4 | 28.58 |
| 12″ | 323.9 | 4.57 | 6.35 | 8.38 | 10.31 | 14.27 | 17.48 | 21.44 | 25.4 | 28.58 | 33.32 |
| 14″ | 355.6 | 6.35 | — | 9.53 | 11.13 | 15.09 | 19.05 | 23.83 | 27.79 | 31.75 | 35.71 |
| 16″ | 406.4 | 6.35 | — | 9.53 | 12.7 | 16.66 | 21.44 | 26.19 | 30.96 | 36.53 | 40.49 |
| 18″ | 457 | 6.35 | — | 9.53 | 14.27 | 19.05 | 23.83 | 29.36 | 34.93 | 39.67 | 45.24 |
| 20″ | 508 | 6.35 | — | 9.53 | 15.09 | 20.62 | 26.19 | 32.54 | 38.1 | 44.45 | 50.01 |
| 24″ | 609.6 | 6.35 | — | 9.53 | 17.48 | 24.61 | 30.96 | 38.89 | 46.02 | 52.37 | 59.54 |
| 26″ | 660.4 | 7.92 | — | 12.7 | 12.7 | 25.4 | 31.75 | 39.67 | 47.63 | 55.58 | 63.5 |
| 28″ | 711.2 | 7.92 | — | 12.7 | 12.7 | 28.58 | 34.93 | 42.88 | 50.8 | 59.54 | 66.68 |
| 30″ | 762 | 7.92 | — | 12.7 | 12.7 | 28.58 | 34.93 | 42.88 | 50.8 | 59.54 | 72.39 |
| 32″ | 812.8 | 7.92 | — | 12.7 | 12.7 | 28.58 | 34.93 | 44.45 | 52.37 | 61.11 | 73.03 |
| 34″ | 863.6 | 7.92 | — | 12.7 | 12.7 | 28.58 | 35.71 | 46.02 | 53.98 | 63.5 | 74.61 |
| 36″ | 914.4 | 7.92 | — | 12.7 | 12.7 | 28.58 | 36.53 | 47.63 | 55.58 | 65.1 | 76.2 |
Stainless Steel SCH Size Comparison Chart
| NPS | OD | SCH 5S | SCH 10S | SCH 40S | SCH 80S |
| 1/2″ | 21.3 | 1.65 | 2.11 | 2.77 | 3.73 |
| 3/4″ | 26.7 | 1.65 | 2.11 | 2.87 | 3.91 |
| 1″ | 33.4 | 1.65 | 2.77 | 3.38 | 4.55 |
| 1-1/2″ | 48.3 | 1.65 | 2.77 | 3.68 | 5.08 |
| 2″ | 60.3 | 1.65 | 2.77 | 3.91 | 5.54 |
| 3″ | 88.9 | 2.11 | 3.05 | 5.49 | 7.62 |
| 4″ | 114.3 | 2.11 | 3.05 | 6.02 | 8.56 |
| 6″ | 168.3 | 2.77 | 3.4 | 7.11 | 10.97 |
| 8″ | 219.1 | 2.77 | 3.76 | 8.18 | 12.7 |
| 10″ | 273 | 3.4 | 4.19 | 9.27 | 15.09 |
| 12″ | 323.9 | 3.96 | 4.57 | 10.31 | 17.48 |
Stainless Steel SCH Size Comparison Chart
SCH vs. O.D.*W.T. (Millimeter System)
The millimeter system is a common notation method used in China, Europe, and for structural piping, typically expressed as outer diameter * wall thickness: 114.3 × 6.0 mm. Its advantage is that wall thickness details can be determined without consulting a table; however, it is used less frequently internationally than the Schedule Dimensions system.
SCH vs. EN/DIN
The EN/DIN European standard commonly uses a notation based on actual dimensions plus material standards, such as: EN 10219 168.3 × 6.3. This notation specifies the actual wall thickness, making it clearer and more straightforward.
In addition to the wall thickness notations mentioned above, the SCH system also includes an older American standard system: STD / XS / XXS. These are also commonly found in Schedule Dimensions tables, where STD corresponds to SCH 40; XS corresponds to SCH 80; and XXS corresponds to thicker pipes. The Schedule system is the most important American standard wall thickness system in the steel pipe industry. It defines dimensions using NPS + SCH and is primarily used for industrial pressure piping, making it an indispensable steel pipe sizing system.
Applications of Different Schedule Grades
SCH 10 (Thin-Wall)
Features:
Thin wall thickness
Low cost
High flow capacity
Applications:
HVAC systems
Low-pressure water distribution
Ventilation ducts
SCH 40 (Standard Grade)
Features:
Most commonly used industrial standard
Balanced overall performance
Applications:
Construction projects
Fire protection systems
General industrial piping
SCH 80 (Heavy-Duty Grade)
Features:
High strength
High pressure resistance
Applications:
Oil and gas
Chemical media
High-temperature steam
SCH 160 (Extra-Heavy-Duty Grade)
Features:
Extremely thick walls
High safety rating
Applications:
High-pressure industrial systems
Special engineering pipelines
Common Ways to Specify SCH Systems in Procurement
When procuring steel pipes, it is not enough to specify just the wall thickness; a complete set of specifications is required. The logical sequence is: diameter, wall thickness, standard, material grade, and length. None of these key elements can be omitted.
Carbon steel pipe specification: 6″ SCH 40 ASTM A106 Gr.B Seamless Pipe.
Structural steel specification: 114.3 × 6 mm S355JRH.
The SCH (Schedule) system is one of the most important wall thickness standard systems in the steel pipe industry. It defines wall thickness grades for different pipe diameters through a unified numbering system, enabling engineering design, procurement, production, and installation to use a common technical language. The SCH system is widely used in the oil and gas, chemical, power, fire protection, and construction sectors. It not only facilitates the rapid matching of pressure ratings and pipe fitting specifications but also effectively reduces communication errors and improves project execution efficiency, serving as a crucial foundation for the standardization of industrial piping systems worldwide.