Steel Pipe Schedule Chart — Dimensions, Wall Thickness, and Weight

Steel pipe is specified by Nominal Pipe Size (NPS) and schedule (wall thickness designation). This chart covers NPS 1/8 through NPS 36, schedules 5S through XXH, with outside diameter, wall thickness, inside diameter, cross-sectional area, moment of inertia, and weight per foot. Structural applications primarily use Schedule 40, Schedule 80, and XH (Extra Heavy).

Structural note: For new structural designs, AISC now recommends ASTM A500 or A1085 HSS (hollow structural sections) over pipe, as HSS have tighter tolerances and higher Fy (50 ksi vs. 35 ksi for A53 pipe). Pipe is still used for utility, process piping, and legacy structures.

Pipe Designation System

NPS (Nominal Pipe Size): Dimensionless number that loosely relates to the bore diameter. For NPS ≥ 14, NPS equals the actual outside diameter in inches.

Schedule: Wall thickness designator. Common schedules:

• Sch 5S / 10S: Thin-wall; stainless applications
• Sch 40 (Std): Standard wall; most common for water/gas service
• Sch 80 (XH): Extra Heavy wall; high-pressure service
• Sch 120 / 160 / XXH: Extra Extra Heavy; high-pressure process

Pipe Grade: ASTM A53 Grade B is the standard structural pipe grade: Fy = 35 ksi, Fu = 60 ksi.

Standard Pipe Schedule Chart — NPS 1/2 to NPS 12

All dimensions in inches; weight in lb/ft.

Large-Diameter Pipe — NPS 14 to NPS 36

For NPS ≥ 14, OD = NPS in inches exactly.

Structural Properties — Selected Pipe Sizes

For pipe used as structural columns (A53 Gr B, Fy = 35 ksi), key section properties:

Pipe vs. HSS: Which to Specify?

Rule: For new structural designs, specify HSS per A500 Grade C or A1085. Use pipe only when you must interface with piping systems, when the pipe is serving a dual structural-utility role, or when replacing existing pipe members.

Metric Pipe Chart — DN Sizes

For DN (Diameter Nominal) pipe per ISO 65 / EN 10255:

Frequently Asked Questions

What is the outside diameter of Schedule 40, 2-inch pipe? The OD of NPS 2 pipe is 2.375 inches for all schedules — the OD does not change between schedules. Only the wall thickness (and therefore ID) changes. Schedule 40 wall = 0.154 in, giving ID = 2.067 in. Schedule 80 wall = 0.218 in, giving ID = 1.939 in.

Why does "2-inch pipe" have an OD of 2.375 inches? The NPS designation is historical. NPS originally referred to the approximate bore (inside diameter) of early iron pipe standards. The OD was set larger to allow machining of threads on the end. When modern pipe schedules were established, OD was fixed so that fittings would be interchangeable across schedules. For NPS ≥ 14, NPS equals the actual OD.

What is the difference between Schedule 40 and Schedule 80? Both have the same OD. Schedule 80 has a thicker wall, smaller bore, and heavier weight. Sch 80 is rated for higher pressure and is used in chemical processing, high-pressure hydraulics, and structural applications where extra wall thickness is needed. Sch 40 is standard for domestic water, fire protection, and light structural use.

What schedule should I use for structural pipe columns? For short columns with moderate loads: Schedule 40 (Standard). For heavier loads or where corrosion allowance is needed: Schedule 80 (XH). For very heavy compression or high axial loads: XXH or consider switching to HSS. Always verify D/t local buckling limits per AISC 360 Section E7 for thin-walled round sections: D/t ≤ 0.15E/Fy ≈ 124 for Fy = 35 ksi.

What is the difference between pipe schedule and wall thickness? Pipe schedule is a dimensionless designator — such as 40, 80, or 160 — that indirectly specifies wall thickness, but the actual wall thickness in inches varies with NPS (nominal pipe size). For example, Schedule 40 wall thickness is 0.154 in for NPS 2 but increases to 0.406 in for NPS 12; the schedule number alone does not uniquely determine the wall thickness without knowing the NPS. The relationship between schedule number and wall thickness was standardized to yield predictable pressure ratings across pipe diameters. Engineers specifying pipe must always state both the NPS and the schedule (or explicit wall thickness) to fully define the section.

When do engineers specify structural pipe rather than HSS round sections? Pipe is retained over HSS round in three main scenarios: when the member must serve a dual structural and utility role (carrying a fluid while also acting as a column or strut), when interfacing with existing pipe systems where NPS-based fittings and couplings are required, or when replacing a deteriorated member in an older structure that was originally designed with pipe. For new standalone structural members, AISC recommends A500 Grade C or A1085 HSS round over A53 pipe because HSS has a higher yield strength (46–50 ksi vs. 35 ksi), tighter wall tolerances (particularly A1085 with its −0/+10% tolerance), and is listed as the preferred round hollow section in AISC 360-22 for seismic applications.

How is pipe nominal diameter different from the actual outside diameter? For NPS 1/8 through NPS 12, the nominal pipe size bears no direct dimensional relationship to either the inside or outside diameter — it is a legacy trade designation inherited from 19th-century iron pipe standards. As an example, NPS 2 pipe has an actual outside diameter of 2.375 inches, not 2 inches, and NPS 1-1/2 has an OD of 1.900 inches. This mismatch exists because the OD was fixed so that threaded fittings would remain interchangeable as wall thickness changed with schedule. Only for NPS 14 and larger does the nominal size equal the actual outside diameter in inches.

Run This Calculation

→ Section Properties Calculator — look up moment of inertia, section modulus, and radius of gyration for round HSS and pipe sections.

→ Beam Capacity Calculator — bending and shear capacity for round HSS or pipe used as structural beams.

Related pages

• HSS Section Properties — AISC round HSS dimension and property tables
• Column Capacity Calculator — axial compression design for pipe and HSS columns
• Steel Section Types — when to use pipe vs. HSS vs. W-shape
• Steel Material Properties — A53, A500, A1085 grade properties
• Reference tables directory — all steel reference tables
• Tools directory — all structural calculators
• How to verify calculator results
• structural steel weight per foot table
• Steel Angle Sizes
• steel member weight calculator

Pipe dimensions per ASME B36.10M (carbon/alloy steel) and B36.19M (stainless). Weights calculated for carbon steel density (490 lb/ft³). Verify exact wall tolerances with mill specifications for critical applications.

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