What does Schedule 40 mean?

Schedule 40 identifies a specific wall thickness for a given NPS under ASME B36.10M. The actual thickness varies by size, for example 0.154 inches at 2 inch NPS and 0.237 inches at 4 inch NPS.

What does Schedule 80 mean?

Schedule 80 identifies a thicker wall than Schedule 40 at the same NPS, for example 0.218 inches at 2 inch NPS compared to 0.154 inches for Schedule 40.

Does a higher pipe schedule mean thicker walls?

Generally yes at a given NPS, higher schedule numbers correspond to thicker walls, though the exact numerical progression and available schedules vary by size.

Does Schedule 40 mean 0.40 inch wall thickness?

No. This is a common misconception. Schedule 40 wall thickness varies by NPS and is never simply 0.40 inches; for example it is 0.109 inches at 1/2 inch NPS and 0.237 inches at 4 inch NPS.

What is the difference between Schedule 40 and Schedule 80?

At the same NPS, Schedule 80 has a thicker wall and smaller inside diameter than Schedule 40, while both share the same outside diameter.

What is the difference between STD and Schedule 40?

STD (Standard Weight) matches Schedule 40 wall thickness for NPS 1/8 through 10, then diverges at NPS 12 and larger, where STD becomes relatively thinner than Schedule 40 at that size.

What is the difference between XS and Schedule 80?

XS (Extra Strong) matches Schedule 80 wall thickness for NPS 1/8 through 8, then diverges at NPS 10 and larger, where XS uses its own fixed wall thickness.

XXS means Double Extra Strong, the heaviest common wall designation under ASME B36.10M, available only within a limited range of NPS sizes.

What is the difference between Schedule 40 and 40S?

Schedule 40 belongs to ASME B36.10M for carbon and alloy steel pipe, while Schedule 40S belongs to ASME B36.19M for stainless steel pipe. The S suffix specifically differentiates B36.19M dimensions from B36.10M, and some values differ between the two standards at certain sizes.

What is the difference between Schedule 80 and 80S?

Schedule 80 is the carbon steel B36.10M designation while 80S is the stainless steel B36.19M designation; they often align at common sizes but are governed by separate standards and should not be assumed identical at every size.

How do I identify a pipe schedule?

Read printed pipe markings if legible, measure wall thickness directly with a caliper or ultrasonic thickness gauge, or measure OD and ID and calculate wall thickness, then compare against the applicable NPS row in the standard dimensional table.

How do I calculate pipe inside diameter from schedule?

Inside diameter equals outside diameter minus two times wall thickness (ID = OD minus 2t), using the OD for that NPS and the wall thickness for the specific schedule.

Does pipe schedule determine pressure rating?

Not by itself. Schedule establishes wall thickness, which is one input into a pressure design calculation that also requires material, grade, temperature, design code, corrosion allowance, and joint efficiency.

What standard defines steel pipe schedules?

ASME B36.10M defines dimensions and schedules for welded and seamless wrought carbon and alloy steel pipe. ASME B36.19M defines the corresponding stainless steel pipe schedules using S suffix designations.

Construction Charts

Pipe Schedule Chart 2026 – NPS to Wall Thickness Reference

August 16, 2026

0 71 14 minutes read

Pipe Schedule Chart: NPS to Wall Thickness Reference | ConcreteCalculate.com

NPS to Wall Thickness Reference (ASME B36.10M)

Pipe Schedule Chart
NPS to Wall Thickness Reference

A pipe schedule is a standardized wall thickness designation tied to a specific NPS, not a universal thickness or pressure value. This chart maps NPS and schedule directly to wall thickness, ID, and weight.

NPS 1/8″ to 24″+Schedule 5 to 160, STD/XS/XXSB36.10M vs B36.19MNPS to DN ConversionUpdated August 2026

Reviewed by Muhammad Ramzan Babar, PhD Researcher & Calculator Developer · View Profile

🚫

Schedule 40 does not mean 0.40 inch wall thickness

This is the single most common misconception about pipe schedules. Schedule is a standardized designation tied to nominal pipe size (NPS); the actual wall thickness varies by size, from 0.109 inches at 1/2 inch NPS to 0.237 inches at 4 inch NPS, both under Schedule 40.

⭐⭐⭐ Pipe Schedule Chart: Quick Reference

Wall thickness in inches by NPS and schedule, per ASME B36.10M.

NPS	DN	OD	Sch 10	Sch 40 / STD	Sch 80 / XS	Sch 160	XXS
1/2″	15	0.840″	0.109″	0.109″	0.147″	0.187″	0.294″
3/4″	20	1.050″	0.113″	0.113″	0.154″	0.218″	0.308″
1″	25	1.315″	0.109″	0.133″	0.179″	0.250″	0.358″
1-1/4″	32	1.660″	0.114″	0.140″	0.191″	0.250″	0.382″
1-1/2″	40	1.900″	0.109″	0.145″	0.200″	0.281″	0.400″
2″	50	2.375″	0.109″	0.154″	0.218″	0.344″	0.436″
3″	80	3.500″	0.120″	0.216″	0.300″	0.438″	0.600″
4″	100	4.500″	0.120″	0.237″	0.337″	0.531″	0.674″
6″	150	6.625″	0.134″	0.280″	0.432″	0.719″	0.864″
8″	200	8.625″	0.148″	0.322″	0.500″	0.906″	0.875″
10″	250	10.750″	0.165″	0.365″	0.593″	1.125″	—
12″	300	12.750″	0.180″	0.375″ / 0.406″	0.500″ / 0.687″	1.312″	—

📌

Standards basis

ASME B36.10M contains the standardized dimensional relationship between NPS, schedule number, and wall thickness for welded and seamless wrought carbon and alloy steel pipe. Note that at NPS 12, STD (0.375 in) and Schedule 40 (0.406 in) diverge, as do XS (0.500 in) and Schedule 80 (0.687 in), a pattern that begins at this size.

⭐⭐⭐ What Is a Pipe Schedule?

Schedule is a wall-thickness designation, not a stand alone measurement or rating.

Schedule number

A standardized code (5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160) that, combined with NPS, identifies a specific wall thickness under ASME B36.10M.

Why schedules exist

Schedules let designers specify a consistent wall thickness system across a huge range of pipe diameters without inventing custom thicknesses for every project.

Core relationship

NPS plus schedule together determine wall thickness; wall thickness combined with the fixed OD for that NPS determines inside diameter; and wall thickness combined with OD determines weight per unit length.

The key clarification

A pipe schedule is a wall-thickness designation associated with a particular nominal pipe size; it is not simply a universal thickness value that applies the same way at every size.

⭐⭐⭐ NPS to DN Pipe Size Chart

NPS (Nominal Pipe Size, inch based) and DN (Diametre Nominal, metric based) both refer to the same underlying pipe size system.

NPS	DN	Actual OD (in)	Actual OD (mm)
1/8″	DN 6	0.405	10.3
1/4″	DN 8	0.540	13.7
3/8″	DN 10	0.675	17.1
1/2″	DN 15	0.840	21.3
3/4″	DN 20	1.050	26.7
1″	DN 25	1.315	33.4
1-1/4″	DN 32	1.660	42.2
1-1/2″	DN 40	1.900	48.3
2″	DN 50	2.375	60.3
2-1/2″	DN 65	2.875	73.0
3″	DN 80	3.500	88.9
4″	DN 100	4.500	114.3
6″	DN 150	6.625	168.3
8″	DN 200	8.625	219.1
10″	DN 250	10.750	273.1
12″	DN 300	12.750	323.9
14″	DN 350	14.000	355.6
16″	DN 400	16.000	406.4
18″	DN 450	18.000	457.2
20″	DN 500	20.000	508.0
24″	DN 600	24.000	609.6

🧮

Quick estimation rule

For a fast approximation, DN is roughly NPS multiplied by 25 (or NPS multiplied by 25.4 for NPS 14 and larger, where OD in mm equals NPS times 25.4 exactly). This rule of thumb works reasonably well above NPS 5, but always use the exact table for precise work, since smaller sizes and 2-1/2, 3-1/2 inch NPS do not follow the simple multiplication exactly.

NPS to DN pipe size comparison showing a 2-inch NPS fitting marked DN 50, with common inch-to-metric pipe size equivalents.

⭐⭐⭐ Pipe Schedule, Outside Diameter & Wall Thickness

The critical geometric relationship behind every schedule table.

📐

OD stays fixed, wall thickness changes

For a given NPS, the nominal outside diameter remains fixed across schedules, while wall thickness changes. For 1/2 inch NPS, OD is 0.840 inches across Schedule 40, 80, and 160 alike; only the wall thickness (and resulting ID) differs between these schedules.

NPS 2 example

OD = 2.375 in, fixed regardless of schedule. Schedule 10: 0.109 in wall. Schedule 40: 0.154 in wall. Schedule 80: 0.218 in wall. Schedule 160: 0.344 in wall.

Inside diameter formula

ID = OD minus 2 times wall thickness. At NPS 2, Schedule 40 gives ID = 2.375 minus 2(0.154) = 2.067 inches; Schedule 80 gives ID = 2.375 minus 2(0.218) = 1.939 inches.

⭐⭐⭐ Complete Pipe Schedule Wall Thickness Chart

The master reference table across common schedules for frequently used NPS sizes.

NPS	OD (in)	Sch 5	Sch 10	Sch 20	Sch 30	Sch 40	Sch 60	Sch 80	Sch 100	Sch 120	Sch 140	Sch 160
1/2″	0.840	0.065	0.109	—	—	0.109	—	0.147	—	—	—	0.187
3/4″	1.050	0.065	0.113	—	—	0.113	—	0.154	—	—	—	0.218
1″	1.315	0.065	0.109	—	—	0.133	—	0.179	—	—	—	0.250
2″	2.375	0.065	0.109	—	—	0.154	—	0.218	—	—	—	0.344
3″	3.500	0.083	0.120	—	—	0.216	—	0.300	—	—	—	0.438
4″	4.500	0.083	0.120	—	—	0.237	—	0.337	—	0.438	—	0.531
6″	6.625	0.109	0.134	—	—	0.280	—	0.432	—	0.562	—	0.719
8″	8.625	0.109	0.148	0.250	0.277	0.322	0.406	0.500	0.594	0.719	0.812	0.906
10″	10.750	0.134	0.165	0.250	0.307	0.365	0.500	0.593	0.719	0.844	1.000	1.125
12″	12.750	0.156	0.180	0.250	0.330	0.406	0.562	0.687	0.844	1.000	1.125	1.312

🚫

Not every schedule exists at every size

Blank cells indicate that schedule is not standardized at that particular NPS. Never assume a schedule exists across the full size range simply because it appears at a nearby size.

⭐⭐⭐ STD, XS & XXS Explained

These are alternative wall designations, related to but not simply synonyms for specific schedules at every size.

Designation	Meaning	Relative Wall	Relative Weight
STD	Standard Weight	Medium	Medium
XS	Extra Strong	Thicker	Higher
XXS	Double Extra Strong	Very thick	Highest

STD vs Schedule 40

STD matches Schedule 40 for NPS 1/8 through 10. At NPS 12 and larger, STD becomes relatively thinner than Schedule 40 at that size (for example, 0.375 in STD versus 0.406 in Schedule 40 at 12 inch NPS).

XS vs Schedule 80

XS matches Schedule 80 for NPS 1/8 through 8. At NPS 10 and larger, XS diverges and uses its own fixed wall thickness (0.500 in XS versus 0.687 in Schedule 80 at 12 inch NPS).

XXS availability

XXS is offered only across a limited NPS range, not the full range covered by Schedule 40, 80, or 160; confirm actual availability for the specific size before specifying.

⚠️

Never assume universal equivalence

Do not state that STD always equals Schedule 40 or that XS always equals Schedule 80 across every NPS; the relationship is size-dependent and diverges at larger diameters.

Comparison of STD, XS, and XXS wall thicknesses for a 2-inch nominal pipe, showing 0.154-inch, 0.218-inch, and 0.344-inch wall thicknesses.

⭐⭐⭐ Schedule 40 vs Schedule 80 vs Schedule 160

Same NPS, same OD, progressively thicker walls and smaller bores.

2 Inch NPS	Wall (in)	ID (in)	Weight (lb/ft)
Schedule 40	0.154	2.067	3.65
Schedule 80	0.218	1.939	5.02
Schedule 160	0.344	1.687	7.46

See the Steel Pipe Weight Chart for the complete lb/ft and kg/m reference across every schedule and NPS.

⭐⭐⭐ Pipe Schedule vs Pressure Rating

This is one of the most important technical distinctions on this page.

🚫

Schedule alone does not determine pressure rating

Schedule establishes wall thickness. Actual pressure capability depends on material, grade, temperature, wall thickness, the applicable design code, manufacturing specification, corrosion allowance, and joint efficiency where applicable, together, not schedule alone. Never state “Schedule 80 is always rated for X psi.”

Does higher schedule mean higher pressure?

Generally, thicker walls can provide greater pressure capacity for a given material and diameter, but schedule alone is not a pressure rating. A full pressure design calculation per the applicable piping code is required for actual service conditions.

Where to find real pressure data

See the Pipe Pressure Rating Chart for the complete material-specific pressure rating framework, including where genuine published ratings exist (such as PVC) versus where calculation is required (such as steel).

⭐⭐⭐ Pipe Schedule vs Weight

Schedule directly determines weight, unlike pressure rating.

🧮

The chain of causation

Higher schedule number leads to greater wall thickness, which leads to more steel cross-sectional area, which leads to higher weight per unit length. This relationship is direct and calculable, unlike the schedule-to-pressure relationship above.

See the Steel Pipe Weight Chart for complete lb/ft and kg/m values, the weight formula, and worked examples.

⭐⭐⭐ Pipe Schedule by NPS

Quick individual reference for the most commonly searched sizes.

2 inch pipe schedule ⭐⭐⭐

OD 2.375 in. Sch 10: 0.109 in wall. Sch 40: 0.154 in wall, 2.067 in ID, 3.65 lb/ft. Sch 80: 0.218 in wall, 1.939 in ID, 5.02 lb/ft. Sch 160: 0.344 in wall, 1.687 in ID, ~7.46 lb/ft.

3 inch pipe schedule ⭐⭐⭐

OD 3.500 in. Sch 40: 0.216 in wall, 7.58 lb/ft. Sch 80: 0.300 in wall, 10.25 lb/ft.

4 inch pipe schedule ⭐⭐⭐

OD 4.500 in. Sch 10: 0.120 in wall. Sch 40: 0.237 in wall, 10.79 lb/ft. Sch 80: 0.337 in wall, 14.98 lb/ft. Sch 160: 0.531 in wall, 22.51 lb/ft.

6 inch pipe schedule ⭐⭐⭐

OD 6.625 in. Sch 10: 0.134 in wall. Sch 40: 0.280 in wall, 18.97 lb/ft. Sch 80: 0.432 in wall, 28.57 lb/ft.

8 inch pipe schedule ⭐⭐⭐

OD 8.625 in. Sch 10: 0.148 in wall. Sch 40: 0.322 in wall, 28.55 lb/ft. Sch 80: 0.500 in wall, 43.39 lb/ft.

12 inch pipe schedule ⭐⭐⭐

OD 12.750 in. Sch 40: 0.406 in wall, 53.53 lb/ft. Sch 80: 0.687 in wall, 88.51 lb/ft. Note STD (0.375 in) and XS (0.500 in) diverge from Sch 40/80 at this size.

📌

Large diameter pipe (14 inch and above)

For NPS 14 and larger, outside diameter in inches equals the nominal size exactly (14 inch NPS has a 14.000 inch OD), unlike smaller NPS sizes where OD is numerically larger than the nominal label. This is a fundamental transition point in the NPS system.

⭐⭐⭐ ASME B36.10M vs B36.19M: Steel vs Stainless Schedules

The S suffix distinguishes an entirely separate stainless steel dimensional standard.

Feature	ASME B36.10M	ASME B36.19M
Primary material	Carbon and alloy steel	Stainless steel
Schedule style	5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160	5S, 10S, 40S, 80S
OD system	NPS based	NPS based (same OD series)
Wall thickness	Schedule dependent	Schedule dependent, per B36.19M’s own table
S suffix	No	Yes

🚫

Schedule 40 is not the same as Schedule 40S

Schedule 40 belongs to ASME B36.10M for carbon and alloy steel. Schedule 40S belongs to ASME B36.19M for stainless steel. The S suffix specifically differentiates B36.19M dimensions from B36.10M, and some B36.19M wall thicknesses differ from the equivalent B36.10M schedule at particular sizes, especially at larger NPS. Always confirm which standard governs the actual material in question rather than assuming interchangeability.

Common alignment at smaller sizes

For many common sizes, 40S wall thickness matches Schedule 40, and 80S matches Schedule 80, within the smaller to mid NPS range.

Divergence at larger sizes

At larger NPS, B36.19M values can differ meaningfully from B36.10M at the nominally equivalent schedule number; always verify the specific size against the current standard rather than assuming universal alignment.

⭐⭐⭐ How to Identify Pipe Schedule

You generally do not calculate a schedule number from scratch; you measure and compare against the standard table.

Read pipe markings.

Check for printed or stamped NPS, schedule, and standard designation.

Measure or obtain wall thickness.

Use a caliper at an accessible cut end, a micrometer for precision, or an ultrasonic thickness gauge for installed or inaccessible pipe.

Identify NPS.

Confirm nominal pipe size from markings or by measuring OD and comparing against the standard NPS table.

Compare with the applicable dimensional standard.

Cross-reference the measured wall thickness against the correct NPS row in ASME B36.10M or B36.19M as appropriate.

Determine schedule.

Identify the matching schedule number for that NPS and wall thickness combination.

Check material standard.

Confirm whether the pipe is carbon steel (B36.10M) or stainless steel (B36.19M) to use the correct comparison table.

⚠️

There is no simple universal schedule formula

There is no formula such as “Schedule = wall thickness times X” that works universally. Schedule is a standardized designation tied to NPS and wall thickness together, requiring comparison against the applicable dimensional standard rather than a calculation from first principles.

⭐⭐ Pipe Schedule and Flow Area

Higher schedule reduces ID and therefore reduces available flow area at the same NPS.

🧮

Flow area formula

Flow area A = πD²/4, using actual inside diameter D. Higher wall thickness means smaller ID, smaller flow area, and potentially greater velocity or pressure loss for the same volumetric flow rate.

2 Inch NPS	ID (in)	Flow Area (in²)
Schedule 40	2.067	3.36
Schedule 80	1.939	2.95

Actual hydraulic design requires flow rate, pipe length, fluid properties, roughness, fittings, and elevation change together; schedule selection alone does not constitute a flow-sizing recommendation.

⭐⭐⭐ This Chart vs Related Pages

Each page in this reference cluster answers a distinct question to avoid overlap.

Page	Primary Focus
Pipe Schedule Chart (this page)	NPS + schedule → wall thickness → ID
Pipe Wall Thickness Chart	Pipe/product → wall thickness across multiple materials (steel, stainless, PVC)
Steel Pipe Weight Chart	NPS + schedule → lb/ft and kg/m weight
Pipe Pressure Rating Chart	Material + size → actual pressure rating and design factors

⭐⭐ Pipe Schedule for Structural Applications

Pipe schedule and structural HSS designation are not automatically interchangeable concepts.

🚫

Do not use process-pipe schedule for structural design without verification

Structural round hollow sections can follow different dimensional and design standards than ASME B36.10M process piping. Confirm the applicable structural specification before using a schedule chart to represent a structural HSS member.

Construction applications ⭐⭐

Water lines, fire protection, industrial piping, construction equipment, pumping systems, and temporary piping all rely on correctly identified pipe schedules for the intended service.

Plumbing and industrial piping

Plumbing uses schedule alongside material selection and local code requirements; industrial process piping additionally requires the applicable design code, pressure, and temperature evaluation.

⭐⭐⭐ Pipe Schedule Visual Guide

Original diagrams explaining the schedule to wall thickness relationship and key comparisons.

Pipe cross-section: OD is fixed for a given NPS, while wall thickness (and therefore ID) changes with schedule.

Same NPS and OD, progressively thicker walls from Schedule 40 through Schedule 160.

Schedule 40 (carbon steel, B36.10M) and Schedule 40S (stainless steel, B36.19M) are governed by different standards.

⭐⭐⭐ Pipe Schedule Worked Examples

These examples demonstrate the lookup and calculation process.

1. Find Wall Thickness

Given: 2 inch NPS, Schedule 40.Result: 0.154 inches, from the standard B36.10M dimensional table.

2. Find Inside Diameter

Given: 2 inch NPS, Schedule 80 (OD 2.375 in, wall 0.218 in).Result: ID = 2.375 minus 2(0.218) = 1.939 inches.

3. Find Schedule From Measured Wall

Given: 2 inch NPS pipe with measured wall thickness of approximately 0.218 inches.Result: this matches Schedule 80 at 2 inch NPS in the standard table.

4. Compare Two Schedules

Given: 4 inch NPS in Schedule 40 and Schedule 80.Result: Sch 40 has 0.237 in wall, 3.998 in ID, 10.79 lb/ft; Sch 80 has 0.337 in wall, 3.826 in ID, 14.98 lb/ft.

5. Convert Wall Thickness to mm

Given: 0.154 inches.Result: 0.154 x 25.4 = 3.912 mm.

⭐⭐⭐ Common Pipe Schedule Mistakes

Most schedule-related errors trace back to one of these misunderstandings.

❌ Thinking Schedule 40 means 0.40 inch wall

Wall thickness varies by NPS; there is no fixed 0.40 inch value.

❌ Assuming higher schedule always means a specific PSI

Pressure capability requires a full design calculation, not a schedule lookup.

❌ Confusing NPS with actual OD

NPS 12 and smaller have an actual OD larger than the nominal number.

❌ Confusing schedule with material grade

Schedule is a dimensional designation; grade describes material strength.

❌ Confusing 40 with 40S

Different governing standards for carbon steel versus stainless steel.

❌ Confusing STD with Schedule 40 at every size

They diverge starting at NPS 12.

❌ Confusing XS with Schedule 80 at every size

They diverge starting at NPS 10.

❌ Mixing B36.10M and B36.19M

Different standards for different materials; do not assume identical values.

❌ Assuming all schedules exist for all NPS sizes

Many schedule/size combinations are simply not standardized.

❌ Using schedule alone to select pressure capability

Material, temperature, and design code are equally essential.

❌ Confusing pipe with tube

Pipe uses NPS/schedule conventions; tube is typically sized directly by OD.

Frequently Asked Questions

A standardized wall thickness designation tied to a specific NPS under ASME B36.10M.

A specific wall thickness for a given NPS; the actual value varies by size.

A thicker wall than Schedule 40 at the same NPS.

Generally yes at a given NPS, though the exact progression varies by size.

No, this is a common misconception; wall thickness varies by NPS.

Same OD, but Schedule 80 has a thicker wall and smaller ID.

They match through NPS 10, then diverge at NPS 12 and larger.

They match through NPS 8, then diverge at NPS 10 and larger.

Double Extra Strong, the heaviest common wall designation, available in a limited size range.

Schedule 40 is B36.10M carbon steel; 40S is B36.19M stainless steel, a separate standard.

Same distinction as 40 vs 40S, applied to the 80 series.

Read markings, measure wall thickness, and compare against the standard table for the identified NPS.

ID = OD minus 2 times wall thickness.

No, not by itself; pressure rating requires a full design calculation.

ASME B36.10M for carbon and alloy steel; ASME B36.19M for stainless steel.

📄 Download Pipe Schedule Chart PDF

This PDF is a genuine field reference. Use the print button to create a print-ready or downloadable version.

NPS, DN, OD referenceSchedule 5 through 160STD, XS, XXS chartWall thickness tableInside diameter chartlb/ft and kg/m noteSchedule 5S/10S/40S/80S noteB36.10M/B36.19M distinctionCommon sizes referenceWorked examples

Cite or Embed This Chart

Copy the page-wide citation to reference the complete Pipe Schedule Chart.

<p>Source: <a href=”https://concretecalculate.com/pipe-schedule-chart”>Pipe Schedule Chart – ConcreteCalculate.com</a></p>

Pipe Schedule ChartNPS to Wall Thickness Reference