Pipe Schedule Chart

A pipe schedule is a standardized system used to define the wall thickness of a pipe. The schedule number does not represent an exact measurement but indicates the relative thickness of the pipe wall for a given Nominal Pipe Size (NPS). Common schedule numbers include Schedule 5, Schedule 10, Schedule 20, Schedule 40, Schedule 80, Schedule 120, and Schedule 160.

Pipe schedules are established by industry standards such as ASME B36.10M and ASME B36.19M to ensure consistency in dimensions, pressure ratings, and performance across different piping systems. Engineers, fabricators and procurement teams use pipe schedules to select the appropriate pipe for specific operating conditions.

Purpose of a Pipe Schedule

The primary purpose of a pipe schedule is to specify wall thickness while maintaining a standard outside diameter (OD) for each pipe size. By varying the wall thickness, manufacturers can produce pipes capable of handling different pressure, temperature and mechanical load requirements.

• Determines pipe wall thickness.
• Helps calculate pressure-handling capability.
• Impacts pipe weight and material cost.
• Ensures compatibility with fittings and flanges.
• Supports compliance with ASME and ASTM standards.

Pipe Schedule Numbering System

As the schedule number increases, the pipe wall becomes thicker. Higher schedule pipes generally provide greater strength and pressure resistance. For example, a Schedule 80 pipe has a thicker wall than a Schedule 40 pipe of the same nominal size.

Although the wall thickness changes with the schedule number, the outside diameter remains constant for the same NPS. The internal diameter decreases as wall thickness increases.

Impact of Pipe Schedule on Strength

Wall thickness directly affects the structural strength and pressure capacity of a pipe. Thicker schedules can withstand higher internal pressures, mechanical stresses and harsh operating conditions. However, they also increase pipe weight and material costs.

For example, a 2-inch Schedule 80 pipe has the same outside diameter as a 2-inch Schedule 40 pipe, but its thicker wall reduces the internal diameter while increasing strength, weight and pressure-handling capability.

The following Pipe Schedule Chart provides standard dimensions for commonly used pipe sizes. It includes Nominal Pipe Size (NPS), Outside Diameter (OD), and wall thickness values for Schedule 5, Schedule 10, Schedule 40, Schedule 80, and Schedule 160 pipes.

Wall thickness values are shown in millimeters (mm). For exact dimensions and tolerances, refer to ASME B36.10M and ASME B36.19M standards.

A pipe schedule number is a standardized designation used to indicate the wall thickness of a pipe. Common schedule numbers include Schedule 5, Schedule 10, Schedule 20, Schedule 40, Schedule 80, Schedule 120, and Schedule 160. As the schedule number increases, the pipe wall becomes thicker, resulting in higher strength, greater pressure resistance, and increased weight.

The schedule number itself is not a direct measurement of wall thickness. Instead, the actual thickness varies depending on the Nominal Pipe Size (NPS). For example, the wall thickness of a 2-inch Schedule 40 pipe is different from that of a 6-inch Schedule 40 pipe.

How Pipe Schedule Numbers Affect Pipe Dimensions

For a given NPS, the outside diameter (OD) remains constant regardless of the schedule. However, increasing the schedule number increases wall thickness and reduces the inside diameter (ID).

The selection of pipe schedule depends on operating pressure, temperature, corrosion allowance, fluid type, and project specifications. Engineers typically select higher schedules for demanding environments such as oil & gas, petrochemical, power generation, and high-pressure process plants.

The chart below illustrates how pipe wall thickness generally increases as the schedule number rises. Higher schedules provide greater pressure resistance, mechanical strength and durability, while also increasing pipe weight and reducing the internal diameter.

As shown above, Schedule 5 and Schedule 10 pipes have relatively thin walls and are commonly used in low-pressure applications. Schedule 40 is the industry standard for general-purpose piping, while Schedule 80 and Schedule 160 pipes are preferred for high-pressure and heavy-duty industrial services.

The following pipe weight chart shows the approximate weight per meter for commonly used Schedule 40 steel pipes. Actual weights may vary depending on material grade, manufacturing standard, and tolerance requirements.

Understanding pipe dimensions is essential when selecting the correct pipe size and schedule for industrial applications. Four key terms are commonly used in piping standards: Nominal Pipe Size (NPS), Outside Diameter (OD), Inside Diameter (ID), and Wall Thickness.

Nominal Pipe Size (NPS)

Nominal Pipe Size (NPS) is a standardized designation used to identify pipe sizes. Although called a "size," NPS is not always equal to the actual outside or inside diameter of the pipe. It serves as a reference system that helps standardize pipe dimensions, fittings, valves, and flanges across the industry.

For example, a 2-inch NPS pipe has an actual outside diameter of 2.375 inches (60.33 mm), regardless of its schedule.

Outside Diameter (OD)

Outside Diameter (OD) is the actual measurement across the outside surface of a pipe. The OD remains constant for a given NPS, even when the schedule number changes. This allows fittings and flanges to remain compatible across different pipe schedules.

For instance, both a 2-inch Schedule 40 pipe and a 2-inch Schedule 80 pipe have the same outside diameter of 60.33 mm.

Inside Diameter (ID)

Inside Diameter (ID) is the diameter of the open flow area inside the pipe. Unlike OD, the ID changes as wall thickness changes. Pipes with thicker walls have a smaller internal diameter, which affects flow capacity.

Wall Thickness

Wall thickness is the distance between the outer surface and inner surface of the pipe. It is determined by the pipe schedule and directly impacts pressure rating, strength, durability, and weight.

Higher schedule pipes such as Schedule 80 and Schedule 160 have thicker walls and can withstand higher operating pressures than lower schedules such as Schedule 5 or Schedule 10.

Example:
OD = 60.33 mm
Wall Thickness = 3.91 mm

ID = 60.33 − (2 × 3.91) = 52.51 mm

Pipe schedule and wall thickness are directly related. As the schedule number increases, the pipe wall becomes thicker. This increases pressure resistance and strength while reducing the internal diameter and increasing pipe weight.

For the same Nominal Pipe Size (NPS), the outside diameter remains unchanged across all schedules. The primary difference is the wall thickness, which affects the pipe's internal diameter, weight, and pressure rating.

Pipe schedule and pressure rating are closely related. In general, pipes with higher schedule numbers have thicker walls, enabling them to withstand higher internal pressures. However, pressure rating is not determined by pipe schedule alone. Factors such as material grade, operating temperature, pipe size, and applicable design codes also affect the maximum allowable pressure.

For the same Nominal Pipe Size (NPS) and material, a Schedule 80 pipe can typically handle higher pressure than a Schedule 40 pipe because of its greater wall thickness. Similarly, Schedule 160 pipes are designed for more demanding high-pressure applications.

ASME B36.10M is the standard covering welded and seamless wrought steel pipe dimensions. It includes carbon steel, alloy steel, and mild steel pipes in schedules such as SCH 10, SCH 20, SCH 40, SCH 80, SCH 120 and SCH 160.

The standard defines outside diameter (OD), wall thickness, and dimensional tolerances for NPS pipe sizes used in industrial piping systems worldwide.

ASME B36.19M covers stainless steel pipe dimensions and schedules including SCH 5S, SCH 10S, SCH 40S, and SCH 80S. The standard is commonly used for grades such as 304, 304L, 316, 316L, 321, and 347H stainless steel pipes.

Compared to ASME B36.10M, this standard focuses specifically on corrosion-resistant stainless steel piping systems used in chemical, pharmaceutical, food processing, and marine industries.

Pipe schedules are used across a wide range of industries to ensure safe operation under varying pressure and temperature conditions.

Kamal Steels is a trusted supplier, stockist and exporter of stainless steel pipes, carbon steel pipes, alloy steel pipes, duplex steel pipes, fittings, flanges and industrial piping products. We provide high-quality materials manufactured according to international standards including ASTM, ASME and API specifications.

With extensive industry experience and a commitment to quality, Kamal Steels serves customers across oil & gas, petrochemical, power generation, water treatment, marine, pharmaceutical and construction industries worldwide.

Our product range includes seamless pipes, welded pipes, tubes, fittings, flanges and piping accessories available in various grades, sizes and schedules to meet diverse project requirements.