Pipe Schedule Chart & Wall Thickness Guide (NPS 1/8″ to 42″)

Pipe schedule refers to the thickness of the pipe for a given Nominal Pipe Size (NPS) and DN (Nominal Diameter) gives the metric designation as found in international standards. The NPS indicates the size of the pipe, however, does not actually match the outside diameter of most sizes. The thickness of the pipe is a key factor since it determines the pressure capacity, mechanical strength, weight, and service life of the pipe. The higher the schedule, the thicker the wall and the higher its resistance to internal pressure, external loading and mechanical stress. Choosing the right schedule depends on the following: operating pressure, temperature, fluid properties, material grade, and relevant design codes. Pipe schedule chart is a tool that will allow comparing wall thicknesses available in NPS size from 1/8″ to 42″.

What is the Pipe Schedule? 

A pipe schedule is a numeric designation that indicates a pipe’s wall thickness, and by extension its resistance to internal pressure and mechanical force, for a given nominal size. The widely cited relationship is Sch = 1000 × (P / S) with P being a working pressure and S being an allowable stress. The higher the required pressure/lower the allowable stress, the higher the schedule. This formula, however, should only be used as a guide to selecting a pipe and not as the only determinant because other variables like temperature, corrosion allowance, material strength, tolerances, etc., also determine pipe thickness. ASME B36.10M is for dimensions of welded and seamless carbon and alloy 20 steel pipe and ASME B36.19M is for the dimensions and schedules of stainless steel pipe.

Comprehensive Pipe Schedule Dimensions Chart

Schedule 40 vs Schedule 80 vs Schedule 160

How to Calculate Pipe Weight per Meter / Foot

The standard formula used to calculate the approximate weight of a carbon steel pipe is:

Weight (kg/m) = 0.02466 × T × (OD − T)

Where T is the pipe wall thickness in mm and OD is the outside diameter in mm.

Example: For a carbon steel pipe with OD = 114.3 mm and T = 6.02 mm:

Weight = 0.02466 × 6.02 × (114.3 − 6.02)
Weight ≈ 16.08 kg/m

Stainless Steel Pipe Weight Formula

For stainless steel, the calculation can be adjusted according to its material density:

Weight (kg/m) = 0.02513 × T × (OD − T)

For the same 114.3 mm OD × 6.02 mm wall:

Weight = 0.02513 × 6.02 × 108.28
Weight ≈ 16.39 kg/m

To convert kg/m to kg/ft, multiply the result by 0.3048. Actual pipe weight can vary slightly due to manufacturing tolerances and material density.

Industrial Applications & Selection Guide

Oil & Gas:

Schedule 40 is suitable for most general piping applications and Schedule 80 or 80 and above is recommended for increased working pressures.

Chemical Processing:

Chemical lines are frequently selected for thicker schedules such as Schedule 80 because of higher pressures, temperatures and corrosive forces.

High-Pressure Steam Lines:

The thickness of the walls of steam pipe is normally determined by the design requirements and a higher schedule is chosen when the steam is under high pressure and temperature.

Structural Fabrication:

The general fabrication use is normally Schedule 40 and Schedule 80 may be more appropriate for added wall thickness and strength.

Industrial Utility Lines:

Schedule 40 is used for water, compressed air and other utility lines where the standard wall thickness is adequate.

Pressure Piping:

The right schedule depends on the working pressure, temperature, grade of material, corrosion allowance and relevant piping standards.