Use this reference when you need to identify the dimensional relationship between NPS 12, DN300, and Schedule 120 steel pipe. The table below is the primary source for drafting, material takeoffs, weight checks, and piping reference work; the notes explain how to interpret those values without confusing nominal size with measured diameter.
Schedule 120 pipe 12 inch (DN300) is a heavy-wall steel pipe size commonly used in piping design, fabrication, drafting, and engineering estimation work. This page provides the standard dimensions, wall thickness, inside diameter, and weight per meter for NPS 12 Schedule 120 pipe based on ASME B36.10.
12 Inch Schedule 120 Pipe Dimensions
- Nominal Pipe Size (NPS): 12 inch
- Diameter Nominal (DN): DN300
- Outside Diameter (OD): 323.9 mm
- Wall Thickness: 25.4 mm
- Inside Diameter (ID): 273 mm
- Pipe Weight: 186.92 kg/m
- Pipe Weight Filled With Water: 245.42 kg/m
- Reference Standard: ASME B36.10
- Pipe Type: Steel Pipe
Schedule 120 Pipe 12 Inch Data Table
| Pipe Size | DN | OD (mm) | Wall Thickness (mm) | ID (mm) | Weight (kg/m) |
|---|---|---|---|---|---|
| 12 inch | 300 | 323.9 | 25.4 | 273 | 186.92 |
What Does Schedule 120 Mean?
Schedule 120 refers to a heavy wall thickness series used for steel pipe under ASME B36.10. For the same nominal pipe size, the outside diameter remains fixed while the wall thickness increases according to the schedule. A thicker wall reduces the inside diameter and significantly increases pipe weight.
Typical Uses of 12 Inch Schedule 120 Pipe
NPS 12 Schedule 120 pipe is commonly referenced for heavy-duty industrial piping systems where high wall thickness is required. It may be used in process piping, plant utility systems, structural loading checks, fabrication work, and engineering applications where pipe strength and wall thickness are more critical than maximum flow area.
Why Pipe Weight Matters
Pipe weight per meter is essential for transport planning, crane lifting studies, support design, structural loading, fabrication estimates, and installation planning. For a 12 inch Schedule 120 pipe, the heavy wall thickness results in much higher installed weight than lighter schedules, so accurate weight data is important for engineering and construction work.
12 Inch Schedule 120 Pipe Calculation Notes
The listed weight is based on standard steel pipe dimensions using the outside diameter and wall thickness of the pipe. Actual product weight may vary slightly depending on manufacturing tolerance, material specification, and supplier standard.
Frequently Asked Questions
What is the outside diameter of 12 inch Schedule 120 pipe?
The outside diameter is 323.9 mm.
What is the wall thickness of DN300 Schedule 120 pipe?
The wall thickness is 25.4 mm.
What is the inside diameter of NPS 12 Schedule 120 pipe?
The inside diameter is 273 mm.
How much does 12 inch Schedule 120 pipe weigh?
The approximate weight is 186.92 kg/m.
Which standard covers this pipe size?
This dimension data is based on ASME B36.10 for steel pipe.
Conclusion
Schedule 120 pipe 12 inch (DN300) has an outside diameter of 323.9 mm, wall thickness of 25.4 mm, inside diameter of 273 mm, and a weight of 186.92 kg/m. It is a useful reference for piping design, fabrication, estimating, and heavy-duty industrial engineering work.
How to Read the Schedule 120 Pipe Data
NPS 12 and DN300 describe the nominal size, not the measured outside or inside diameter. For this pipe, the outside diameter is the schedule-independent dimension shown in the source data, while Schedule 120 identifies the heavy-wall series and its associated wall thickness. The inside diameter is then reduced relative to lighter-wall pipe of the same nominal size.
OD, wall thickness, and ID in drawings
Outside diameter is commonly used for layout, fittings, clamps, supports, and clearance checks. Wall thickness is important when reviewing fabrication details, pipe ends, bevel preparations, and weight estimates. Inside diameter is the more relevant dimensional reference for flow-area discussions, but it should not be treated as a substitute for a project-specific hydraulic calculation.
Using the weight data in engineering work
The listed pipe weight can support preliminary material estimates, handling plans, support-load reviews, and installation planning. For assemblies, account separately for fittings, flanges, valves, coatings, insulation, contents, and any project-specific allowances. The filled-with-water value in the source table is useful for a basic contents-loaded comparison, but final support and structural checks require the applicable design conditions.
Schedule does not establish pressure design by itself
Schedule 120 identifies a dimensional wall series; it does not, by itself, establish an allowable pressure, temperature limit, corrosion allowance, or suitability for a particular service. Those decisions depend on the material specification, design code, joining method, manufacturing requirements, operating conditions, and engineering verification.
Related reference topics
For broader design work, connect this page with the site’s pipe schedule reference, NPS and DN size guide, steel pipe weight reference, pipe wall thickness terminology, and DWG pipe detail resources. These related references help readers move from dimensional identification to drafting, estimating, and design review.
Additional Questions About 12 Inch Schedule 120 Pipe
Are NPS 12 and DN300 interchangeable descriptions?
They are the nominal size designations used for the same pipe size in this reference. They do not mean that the measured diameter is exactly 12 inches or exactly 300 millimeters.
Does a thicker schedule change the outside diameter?
For the same nominal pipe size, the outside diameter remains fixed in the schedule system while increased wall thickness reduces the inside diameter and increases pipe weight.
Can the listed weight be used for a final support design?
It can support preliminary checks, but a final support or structural design should also consider the complete piping assembly, contents, insulation, attachments, operating cases, and applicable engineering requirements.
What should be checked before ordering this pipe?
Confirm the nominal size, schedule, material specification, manufacturing requirements, end preparation, applicable project standard, quantity basis, and required certification with the purchase and engineering documents.