Schedule 40 vs Schedule 80 Pipe: Wall Thickness Standards Explained

Introduction to Pipe Schedules

Pipe schedule numbers indicate wall thickness, directly relating to pressure rating and mechanical strength. Schedule 40 and Schedule 80 are the most common schedules, with significant differences in dimensions and applications.

Wall Thickness Comparison by Pipe Size

NPS (in)	OD (mm)	Schedule 40	Schedule 80	Thickness Diff.
1/2″	21.3	2.77 mm (0.109″)	3.73 mm (0.147″)	0.96 mm
3/4″	26.7	2.87 mm (0.113″)	3.91 mm (0.154″)	1.04 mm
1″	33.4	3.38 mm (0.133″)	4.55 mm (0.179″)	1.17 mm
1-1/2″	48.3	3.68 mm (0.145″)	5.08 mm (0.200″)	1.40 mm
2″	60.3	3.91 mm (0.154″)	5.54 mm (0.218″)	1.63 mm
3″	88.9	5.49 mm (0.216″)	7.62 mm (0.300″)	2.13 mm
4″	114.3	6.02 mm (0.237″)	8.56 mm (0.337″)	2.54 mm
6″	168.3	7.11 mm (0.280″)	10.97 mm (0.432″)	3.86 mm
8″	219.1	8.18 mm (0.322″)	12.70 mm (0.500″)	4.52 mm

Weight Comparison (kg/m)

NPS (in)	OD (mm)	Sch 40 Weight	Sch 80 Weight	Weight Increase
1/2″	21.3	1.27 kg/m	1.62 kg/m	+28%
1″	33.4	2.50 kg/m	3.23 kg/m	+29%
2″	60.3	5.44 kg/m	7.48 kg/m	+37%
4″	114.3	16.08 kg/m	22.32 kg/m	+39%
6″	168.3	28.26 kg/m	42.56 kg/m	+51%
8″	219.1	42.55 kg/m	64.64 kg/m	+52%

Pressure Rating Comparison (ASME B31.3)

For ASTM A53 Grade B pipe at various temperatures:

NPS	Schedule	@ 100°C	@ 200°C	@ 300°C	@ 400°C
Allowable Stress (MPa)
A53 Gr B		138	124	110	96
Design Pressure (MPa) – 2″ NPS
2″	40	8.9	8.0	7.0	6.2
2″	80	13.5	12.1	10.7	9.3
Design Pressure (MPa) – 4″ NPS
4″	40	5.7	5.1	4.5	4.0
4″	80	9.5	8.5	7.5	6.6

Flow Capacity Comparison

Using Hazen-Williams formula, relative flow capacity:

NPS	Sch 40 ID (mm)	Sch 80 ID (mm)	Sch 40 Flow	Sch 80 Flow
1/2″	15.8	13.8	100%	76%
1″	26.6	24.3	100%	84%
2″	52.5	49.2	100%	88%
4″	102.3	97.2	100%	90%
6″	154.1	146.4	100%	90%

Application Scenarios

Schedule 40 Applications

• Low-pressure water supply
• Compressed air systems (to 150 psi)
• Fire sprinkler systems
• Drain, waste, and vent (DWV)
• HVAC condensate lines
• General plumbing
• Instrument air

Schedule 80 Applications

• High-pressure water systems
• Steam and condensate (high pressure)
• Chemical processing
• Oil and gas facilities
• Power plant piping
• Refinery applications
• Process piping (Class 300+)

Cost Comparison

NPS	Sch 40 Price Index	Sch 80 Price Index	Premium %
1/2″	100%	130%	+30%
1″	100%	135%	+35%
2″	100%	145%	+45%
4″	100%	155%	+55%
6″	100%	165%	+65%

Selection Guidelines

Choose Schedule 40 when:

• Pressure requirements below 1,000 psi
• Standard commercial applications
• Cost optimization is important
• Maximum flow capacity needed
• NPS 2″ and above for standard service
• Fire protection (NFPA 13 compliant)

Choose Schedule 80 when:

• Pressure requirements exceed 1,000 psi
• Process piping with higher class rating
• Smaller diameter with high pressure
• Steam or high-temperature service
• Chemical or corrosive service
• Reduced flow is acceptable

Weight Calculation Formula

For carbon steel pipe weight (kg/m):

Weight = 0.02466 × (OD - t) × t

Where:
OD = Outside Diameter (mm)
t = Wall Thickness (mm)
0.02466 = Carbon steel factor

Schedule 40 and Schedule 80 Pipe Available from CREATEEL

We stock and produce Schedule 40 and Schedule 80 carbon steel pipe across the full NPS range, in both welded (ERW) and seamless construction, per ASTM A53, ASTM A106, API 5L, and ASME B36.10M. Stainless steel Sch 40/80 is also available in grades 304/L and 316/L.

NPS	OD (mm)	Sch 40 Wall (mm)	Sch 80 Wall (mm)	Product Options
1/2″	21.3	2.77	3.73	ERW, galvanized, seamless
1″	33.4	3.38	4.55	ERW, galvanized, seamless
2″	60.3	3.91	5.54	ERW, galvanized, seamless A106
4″	114.3	6.02	8.56	ERW, seamless A106/A53, API 5L Gr.B
6″	168.3	7.11	10.97	ERW, seamless, API 5L Gr.B/X42/X52
8″	219.1	8.18	12.70	ERW, seamless, SSAW
10″	273.0	9.27	15.09	ERW, SSAW, seamless
12″	323.8	9.53 (XS) / 10.31	17.48	ERW, SSAW, seamless
16″ – 24″	406.4 – 609.6	9.53 – 14.27	See ASME B36.10M	SSAW, LSAW, seamless (up to 24″)

Answers to Common Questions

Q1: Can Schedule 40 pipe handle steam?

A: Schedule 40 is typically limited to 180-200 psi saturated steam. For higher pressure steam, Schedule 80 or extra strong pipe is required.

Q2: What is the pressure rating difference between Sch 40 and Sch 80?

A: Approximately 50-60% higher for Schedule 80 compared to Schedule 40, depending on pipe size and temperature.

Q3: Does Schedule 80 cost twice as much as Schedule 40?

A: Not typically twice, but Schedule 80 costs 30-65% more depending on pipe size, due to more material and slightly different manufacturing.

Q4: Can I use Schedule 40 fittings with Schedule 80 pipe?

A: Yes, standard threaded or flanged fittings are compatible as long as the pipe size (NPS) matches. Pressure rating will be limited by the lower-rated component.

Q5: What happens if I use Sch 40 where Sch 80 is required?

A: The pipe may fail prematurely due to insufficient wall thickness for the pressure, potentially causing safety hazards. Always verify pressure requirements.