ASME B36.10 Steel Pipe Schedule Charts

ASME B36.10 is the standard that defines the outside diameter and wall thickness of welded and seamless wrought steel pipe. A pipe schedule chart is the lookup table that turns a nominal pipe size (NPS) and a schedule number into the actual wall thickness, outside diameter, and weight of the pipe.

On this page you will find the complete ASME B36.10 steel pipe schedule charts for NPS 1/8 through NPS 48, plus a plain-language guide to reading schedule codes, choosing the right wall thickness, and understanding how schedule relates to pressure. All dimensions are shown in both inches and millimetres. For stainless steel equivalents, see the ASME B36.19 dimension charts.

Quick answer: Schedule is a wall-thickness series, not a measurement. For any given NPS, a higher schedule means a thicker wall and - with the same material - a higher pressure rating. The outside diameter for NPS 14 and larger stays constant; only the wall changes.

What Is ASME B36.10 and What Does It Cover?

ASME B36.10 defines the dimensions of wrought steel pipe - its outside diameter, wall thickness for each schedule, and weight - but it does not set pressure ratings or material grades. Those come from separate piping and material standards.

The standard, titled Welded and Seamless Wrought Steel Pipe, covers pipe in sizes from NPS 1/8 (Nominal Pipe Size) through NPS 48 in the dimensional tables presented here. It applies to both welded (for example electric-resistance-welded) and seamless pipe made from carbon and alloy steel. The standard establishes a consistent set of outside diameters and a schedule system so that fittings, flanges, and valves from different makers can interconnect.

It is important to understand what B36.10 is not. It is a dimensional standard, not a pressure standard and not a material standard. The allowable pressure of a given pipe is calculated under a piping code such as ASME B31.3 using the material's allowable stress at temperature. The material grade itself is specified by ASTM product standards such as A106, A53, or API 5L, which we cover later in this guide.

What Does "Pipe Schedule" Mean?

Pipe schedule is a dimensionless index that groups wall thicknesses. A higher schedule number means a thicker wall for the same nominal pipe size, which raises the pipe's pressure capacity and its weight.

Schedules were introduced in the 1930s-40s to standardise wall thickness as mills moved from the old 'standard weight', 'extra strong', and 'double extra strong' names toward a numbered system. Today the common B36.10 schedules are 10, 20, 30, 40, 60, 80, 100, 120, 140, and 160, with STD, XS, and XXS as legacy equivalents (STD roughly equals Schedule 40, XS roughly equals Schedule 80).

A frequent point of confusion is that the schedule number is not a thickness in inches or millimetres, and the same schedule does not give the same wall across different sizes. For a 1 inch pipe, Schedule 40 wall is 0.133 in (3.38 mm); for a 12 inch pipe, Schedule 40 wall is 0.375 in (9.53 mm). The number is a label for a position in a thickness series, not a measurement you can read directly off the pipe.

How Do You Read the Wall Thickness Code on a Pipe?

To read a pipe's wall thickness, decode the stamped marking for its nominal size and schedule, then look up that NPS + schedule pair in the ASME B36.10 chart to read the wall thickness (in and mm) and the weight. The schedule on the pipe is the code; the chart converts it to an actual dimension.

A typical pipe marking reads something like: NPS 6 SCH 40 ASTM A106 GR B. Breaking that down:

1. NPS 6 - the nominal pipe size (approximately 6 inches). Look in the NPS column of the chart.

2. SCH 40 - the schedule code, the wall-thickness series. Find the row for Schedule 40 under that NPS.

3. Read the wall - at NPS 6, Schedule 40 the chart gives a wall of 0.280 in (7.11 mm) and a weight of 18.97 lb/ft (28.23 kg/m).

4. Confirm by measuring - on an existing pipe, measure the outside diameter with a tape and the wall with an ultrasonic gauge; then match both to the chart to confirm the schedule.

Two rules make the code readable. First, NPS is not the outside diameter. For NPS 1/8 through 12, the OD is larger than the nominal number (NPS 1 = 1.315 in OD; NPS 12 = 12.750 in OD). For NPS 14 and larger, the OD equals the nominal number exactly (NPS 14 = 14.000 in OD). Second, the international 'DN' (Diamètre Nominal) is simply NPS x 25.4 mm, so NPS 6 is about DN150. With these two rules and the chart below, any wall-thickness code becomes a concrete dimension.

ASME B36.10 Steel Pipe Schedule Charts

The tables below present the complete dimensional specifications for ASME B36.10 steel pipe. For NPS 14 and larger the outside diameter is constant for each nominal size, so only the wall thickness changes with schedule.

All dimensions are presented in both metric (millimetres, kg/m) and imperial (inches, lb/ft) units. Use the charts to confirm wall thickness, outside diameter, and weight for any NPS and schedule combination.

Need only the most common sizes? See the Sch 40 steel pipe dimensions and weight and Schedule 80 steel pipe dimensions and weight guides for focused charts.

The following tables present the complete dimensional specifications for steel pipe as outlined in ASME B36.10. All dimensions are presented in both metric (millimeters) and customary (inches) units to facilitate international application.

Standard Pipe Schedules Explained

The schedules in common use run from thin-wall 10 up to heavy-wall 160 and XXS; Schedule 40 (Standard) and Schedule 80 (Extra Strong) are the workhorses of general piping.

Each schedule is a band of wall thickness. As a rule of thumb, the higher the number, the thicker and heavier the pipe and the higher its pressure capability for a given material:

How Does Schedule Relate to Pressure Rating?

Schedule controls wall thickness, and wall thickness controls pressure capacity - but the actual allowable pressure also depends on the pipe material and the service temperature, not on the schedule alone.

The piping code formula (simplified, ASME B31.3) is: P = 2 * S * E * t / (D - 2*y*t), where P is allowable pressure, S is the material's allowable stress at temperature, E is the quality factor (1.0 for seamless), t is the wall thickness, and D is the outside diameter. Because S varies by material, two pipes of the same NPS and schedule - say carbon steel versus 316 stainless - will carry different pressures. Schedule 40 and 80 are the standard reference points, but the rating is always a material-and-temperature calculation, never a property of the schedule number by itself.

For deeper reading on the pressure side, see the Schedule 80 steel pipe strength and Schedule 80 pressure rating, price and properties articles.

ASME B36.10 vs ASME B36.19 - Which Standard Applies?

Use ASME B36.10 for carbon and alloy steel pipe, and ASME B36.19 for stainless steel pipe. The two standards share the same NPS/OD logic but use different schedule series and wall thicknesses.

B36.19 stainless pipe uses the 'S' schedule series (5S, 10S, 40S, 80S) with thinner walls than the equivalent B36.10 schedule, because stainless is stronger and corrosion allowance is often built in differently. If you are specifying stainless, you will usually reference B36.19 even though the size logic looks familiar. The chart below summarises the split.

Materials and Grades Used with B36.10 Pipe

ASME B36.10 sets the shape; the material grade is set by a separate ASTM or API product standard. Carbon steel is most common, but the same dimensional system carries alloy, stainless, duplex, and nickel alloys.

JN Alloy supplies the full range - from carbon and alloy steel pipe to stainless steel pipe, duplex steel pipe, and nickel-alloy and Hastelloy pipe - all cut and processed to ASME B36.10 dimensions.

How to Choose the Right Schedule for Your Application

Choose the schedule from the required pressure and temperature, the needed corrosion allowance, and any mechanical loads. When nothing special applies, Schedule 40 is the safe default; move to Schedule 80 when pressure, abrasion, or corrosion margin demands more wall.

• Pressure / temperature: calculate the required wall with the ASME B31.3 formula using your material's allowable stress; pick the next standard schedule up.

• Corrosion allowance: if the fluid will thin the wall over time, start with a heavier schedule (e.g., 80 instead of 40) so the pipe still meets minimum wall at end of life.

• Mechanical load: for spans, supports, and external loads, the heavier wall of Schedule 80 or 160 adds stiffness.

• Cost and weight: heavier schedules cost more and weigh more; over-specifying wastes money and complicates support design.

If you are deciding between the two most common options, the difference between Schedule 40 and Schedule 80 stainless steel pipe article breaks down the trade-offs. Pair the pipe with the right butt-weld fittings and flanges for a complete, standards-matched system.

Frequently Asked Questions

What is ASME B36.10?

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