Schedule 20 Steel Pipe Pressure Rating Chart

How much pressure can Schedule 20 steel pipe handle?
There is no single PSI value for all Schedule 20 steel pipes. The pressure capacity depends on the pipe size, outside diameter, wall thickness, steel grade, operating temperature, corrosion allowance, and applicable design code.For carbon and alloy steel pipe, Schedule 20 is a dimensional designation rather than a standalone pressure class. Under ASME B36.10M, Schedule 20 dimensions vary with nominal pipe size. For example, NPS 8 Schedule 20 has a 0.250-inch wall, while NPS 14 has a 0.312-inch wall.

This guide provides a practical Schedule 20 steel pipe pressure rating reference chart, explains the pressure calculation, and shows why pressure ratings found online can differ.

Schedule 20 Steel Pipe Pressure Rating Chart

The table below uses Schedule 20 dimensions for carbon and alloy steel pipe based on ASME B36.10M. The pressure column is presented as an illustrative hoop-stress reference using an assumed allowable stress of 20,000 psi and the simplified Barlow relationship:
P = 2St / D
It does not represent a universal ASME allowable working pressure.

NPS	DN	OD (in.)	Wall Thickness (in.)	Reference Pressure* (psi)
8	200	8.625	0.25	1,159
10	250	10.75	0.25	930
12	300	12.75	0.25	784
14	350	14	0.312	891
16	400	16	0.312	780
18	450	18	0.312	693
20	500	20	0.375	750
22	550	22	0.375	682
24	600	24	0.375	625
26	650	26	0.5	769
28	700	28	0.5	714
30	750	30	0.5	667
32	800	32	0.5	625
34	850	34	0.5	588
36	900	36	0.5	556

Illustrative reference only, calculated with S = 20,000 psi, nominal wall thickness and outside diameter. Actual allowable working pressure must be determined using the applicable material specification, design code, temperature, weld requirements, corrosion allowance and other project conditions.
The underlying Schedule 20 dimensions are consistent with published ASME B36.10M dimension tables.

A larger pipe does not automatically have a higher pressure rating.
Pressure capacity is strongly influenced by the ratio between wall thickness and pipe diameter. For example, NPS 8 Schedule 20 has a 0.250-inch wall, while NPS 24 has a 0.375-inch wall. Although the larger pipe has a thicker wall, its diameter increases much more significantly.
This is why pipe size, wall thickness and material grade must be considered together when evaluating pressure service.

What Is the Pressure Rating of Schedule 20 Steel Pipe?

Schedule 20 steel pipe does not have one fixed pressure rating.
The term Schedule 20 identifies a wall-thickness series. It does not mean that every Schedule 20 pipe is rated for the same pressure.
The actual pressure capacity depends on:
Nominal pipe size
Outside diameter
Wall thickness
Steel grade
Allowable stress
Operating temperature
Corrosion allowance
Manufacturing method
Weld efficiency, where applicable
Applicable piping design code

ASTM A53 Grade B steel has minimum yield strength of 35,000 psi and minimum tensile strength of 60,000 psi. ASTM A106 Grade B has the same minimum yield and tensile strength values.However, yield strength is not the same as allowable design stress. Therefore, it would be incorrect to use 35,000 psi directly as the allowable pressure stress.This distinction is one of the most important points when interpreting a Schedule 20 pressure chart.

How to Calculate Schedule 20 Steel Pipe Pressure Rating

A simplified method for estimating internal pressure is the Barlow formula:
P = 2St / D
Where:
P = internal pressure
S = allowable stress of the pipe material
t = nominal wall thickness
D = outside diameter
All three pressure variables should use compatible units.
For pressure in psi:
S should be in psi
t should be in inches
D should be in inches
Example: NPS 8 Schedule 20 Steel Pipe
Suppose:
NPS = 8
OD = 8.625 in.
Wall thickness = 0.250 in.
Assumed allowable stress = 20,000 psi
Then:
P = 2 × 20,000 × 0.250 / 8.625
P ≈ 1,159 psi
This is an illustrative calculation, not a certified allowable working pressure.

The calculation demonstrates why simply searching for “Schedule 20 PSI” is insufficient. Change the material stress, temperature, wall thickness or corrosion allowance, and the resulting pressure changes.

What Factors Affect Schedule 20 Pipe Working Pressure?

1.Pipe Diameter
For a given wall thickness and allowable stress, a larger diameter generally produces a lower pressure capacity.
This follows directly from the denominator in the Barlow formula:
P = 2St / D
As D increases, calculated pressure decreases.

2.Wall Thickness
Wall thickness has a direct effect on pressure capacity.
A thicker wall provides greater resistance to internal hoop stress.
For example, increasing wall thickness from 0.250 inch to 0.375 inch increases the calculated pressure capacity when diameter and allowable stress remain unchanged.
This is why Schedule 40 generally has a higher pressure capacity than Schedule 20 for comparable pipe sizes and materials.

3.Steel Grade
The steel grade determines the mechanical properties used in design.
ASTM A53 Grade B, for example, has minimum yield strength of 35,000 psi and tensile strength of 60,000 psi.ASTM A106 Grade B also specifies minimum yield strength of 35,000 psi and tensile strength of 60,000 psi.But these values should not simply be inserted into a working-pressure calculation as the allowable stress.

4.Operating Temperature

Steel strength and allowable design stress can change with temperature.A pressure calculation performed at room temperature may not apply to a high-temperature process line.For steam, hot oil, process gas or other elevated-temperature applications, use the applicable design code and material tables.

5.Corrosion Allowance
Corrosion is another factor that is often overlooked in simple online pressure calculators.If corrosion reduces the effective wall thickness, the remaining pressure capacity also decreases.For example, a nominal 0.250-inch wall does not necessarily provide 0.250 inch of effective structural thickness throughout the entire service life.

6.Manufacturing Tolerance
Nominal wall thickness is not always the minimum measured wall thickness.For ASTM A106, for example, the specified minimum wall thickness at any point is based on a permitted negative tolerance from the nominal wall.For a real pressure design, this difference should not be ignored.

Schedule 20 Steel Pipe Pressure Rating vs Burst Pressure

Working pressure and burst pressure are not the same thing.
Working pressure is the pressure at which a system is designed to operate safely under specified conditions.
Burst pressure refers to a much higher pressure associated with structural failure.
A pipe should never be selected by taking a published burst pressure and treating it as the allowable working pressure.
A proper design considers:
Design pressure
Design temperature
Material properties
Wall thickness
Safety requirements
Corrosion allowance
Applicable code
Component ratings
This distinction is especially important for buyers who compare pressure values from different online charts.

Schedule 20 vs Schedule 40 Pressure Rating

Schedule 20 and Schedule 40 should not be compared only by their schedule numbers.
For the same nominal size and material, Schedule 40 generally has a thicker wall than Schedule 20 and therefore a higher pressure capacity.

Feature	Schedule 20	Schedule 40
Wall thickness	Lower	Higher
Weight	Lower	Higher
Material usage	Lower	Higher
Pressure capacity	Generally lower	Generally higher
Typical use	Lower-pressure service	Wider pressure range
High-pressure suitability	Limited	Better, depending on design
Cost	Often lower	Often higher

However, Schedule 40 is not automatically suitable for every high-pressure application. The final selection still depends on material, temperature, code and design pressure.
This creates a natural internal link to your Schedule 40 Pipe Pressure Rating article.

Is Schedule 20 Steel Pipe Suitable for High-Pressure Applications?

Schedule 20 steel pipe can be used in pressure-containing systems, but it should not be selected simply because it is labeled “steel pipe.”
Its suitability depends on the required design pressure and all applicable design conditions.
Schedule 20 may be considered when:
The design pressure is relatively low.
The required pipe diameter is large.
Weight reduction is important.
The applicable design code permits the selected wall thickness.
The material grade meets the project requirements.
For high-pressure applications, engineers may select a thicker wall such as Schedule 40, Schedule 80 or another specified wall thickness.
The correct choice should always start with the design pressure, not the Schedule number.