Pipe Size, Schedule & Material Grade Reference
Engineering reference for NPS/DN conversion, carbon-steel pipe outside diameter, schedule wall thickness, calculated inside diameter, steel weight, internal volume and commonly used ASME, ASTM, API and EN piping standards.
Steel Pipe Schedule & Dimension Calculator
Select the pipe size and an available wall designation. The calculator returns dimensional and estimated quantity information useful for piping, chilled-water, district-cooling and mechanical works. For NPS 40–48, use the custom-wall option when a project-specific thickness is required.
Custom Wall Thickness Calculator
For project-specific pipe thicknesses, fabricated pipe or sizes where the desired schedule is not included above, enter OD and wall thickness directly.
NPS, DN, OD and Schedule — What They Mean
NPS — Nominal Pipe Size
NPS is a dimensionless nominal size designation. It is not generally equal to the actual outside or inside diameter. A selected NPS corresponds to a standardized outside diameter.
DN — Diameter Nominal
DN is the metric nominal designation corresponding approximately to the NPS series. For example, NPS 10 is commonly designated DN 250; DN is not a direct measured diameter.
Pipe Schedule
Schedule identifies a standardized wall-thickness series. For the same NPS, increasing wall thickness reduces the inside diameter because the outside diameter remains fixed.
STD, XS and XXS
Standard Weight, Extra Strong and Double Extra Strong are historical wall designations. STD and XS coincide with numbered schedules only over part of the size range, so they should not be treated as universal synonyms for Sch 40 and Sch 80.
Common NPS to DN and Outside Diameter Reference
| NPS | DN | OD (mm) | NPS | DN | OD (mm) |
|---|
Important ASME Piping Standards
| Standard | Area | Practical Use |
|---|---|---|
| ASME B36.10M | Welded and seamless wrought steel pipe dimensions | Primary dimensional reference for carbon and alloy steel pipe OD, wall/schedule and mass. |
| ASME B36.19M | Stainless steel pipe dimensions | Dimensional reference commonly associated with 5S, 10S, 40S and 80S stainless-steel schedules. |
| ASME B16.5 | Pipe flanges and flanged fittings | Flange dimensions, pressure-temperature ratings and related requirements within its size/class scope. |
| ASME B16.47 | Large-diameter steel flanges | Large-bore flange dimensional/rating reference. |
| ASME B16.9 | Factory-made wrought butt-welding fittings | Elbows, tees, reducers and other butt-weld fittings. |
| ASME B16.11 | Forged fittings | Socket-weld and threaded forged fittings. |
| ASME B31.1 | Power piping | Design and construction rules for piping within the code's power-piping scope. |
| ASME B31.3 | Process piping | Widely used for refinery, chemical, process and industrial piping systems. |
| ASME B31.9 | Building services piping | Building-service piping applications within the code's stated scope. |
Common ASTM Material Specifications
| Component | Common ASTM Specification | Typical Engineering Reference |
|---|---|---|
| Seamless carbon-steel pipe | ASTM A106 / A106M — Grades A, B, C | High-temperature-service carbon steel pipe; Grade B is frequently encountered in industrial piping. |
| Steel pipe | ASTM A53 / A53M | Pipe specification covering types/grades and manufacturing routes defined by the standard. |
| Low-temperature pipe | ASTM A333 / A333M | Seamless and welded steel pipe intended for low-temperature service; Grade 6 is a common project grade. |
| Stainless-steel pipe | ASTM A312 / A312M | Austenitic stainless piping such as TP304/304L and TP316/316L depending on service requirements. |
| Butt-weld fittings | ASTM A234 / A234M WPB | Common carbon-steel wrought butt-welding fitting material. |
| Forged flanges/fittings | ASTM A105 / A105M | Common forged carbon-steel pressure-piping component material. |
| Alloy-steel bolting | ASTM A193 / A193M B7 | Frequently used high-strength stud-bolt material for flanged joints. |
| Nuts | ASTM A194 / A194M 2H | Common nut grade paired with B7 bolting where permitted by the project specification. |
API and EN / European Piping References
API 5L — Line Pipe
API 5L is widely used for line pipe in pipeline transportation systems. Grades and product specification levels must be selected from the applicable project design basis; an API grade is not automatically interchangeable with an ASTM piping grade.
EN 10216 — Seamless Tubes for Pressure Purposes
The EN 10216 family covers seamless steel tubes for pressure purposes, with separate parts for room-temperature, elevated-temperature, fine-grain, low-temperature and stainless-steel applications.
EN 10217 — Welded Tubes for Pressure Purposes
The EN 10217 family addresses welded steel tubes for pressure purposes, with parts differentiated by material, manufacturing route and temperature/service properties.
EN 1092-1 — Flanges
European PN-designated circular flange systems differ from ASME Class flange systems. Do not assume PN and ASME Class values or dimensions are directly interchangeable.
EN 10204 — Inspection Documents
Commonly referenced for metallic-product inspection documentation such as 3.1 and 3.2 certificates. The required certificate type should be stated in the purchase specification.
EN vs ASME / ASTM
EN materials and dimensions use their own designations and requirements. Equivalent-looking grades should not be substituted solely by comparing chemistry or strength; the governing design code and project approval control acceptance.
How ASME, ASTM, API, EN and ISO Differ
| Organization / System | Main Role in Piping | Example |
|---|---|---|
| ASME | Design/construction codes plus dimensional and component standards. | B31.3 process piping; B36.10M pipe dimensions; B16.5 flanges. |
| ASTM International | Material/product specifications and test requirements. | A106 pipe, A234 fittings, A105 forgings, A193 bolting. |
| API | Petroleum, natural-gas and pipeline industry standards/specifications. | API 5L line pipe. |
| EN | European standards adopted by CEN members. | EN 10216 seamless pressure tubes; EN 1092-1 flanges. |
| ISO | International standards across industries; may be adopted nationally or referenced by project specifications. | Application depends on the specific ISO document and project basis. |
Useful Pipe Engineering Calculations
Approximate Steel Pipe Weight
OD and t in millimetres; based on an approximate carbon-steel density of 7,850 kg/m³.
Internal Water Volume
ID in millimetres. Useful for flushing volume, hydrotest water, chemical dosing and chilled-water system estimates.
Flow Area
Use consistent units. Actual hydraulic sizing must also consider velocity, friction loss, fittings, valves and available pressure.
Filled Pipe Weight
For water, 1 litre is approximately 1 kg near normal ambient conditions. Use actual fluid density when required.
Material Selection Is Not Based on Size Alone
Pipe schedule and material grade must be selected from the design conditions, including design pressure and temperature, fluid, corrosion allowance, joining method, design code, mechanical loads, insulation/service environment, testing requirements and approved project specification. The tables above are references, not automatic material-selection rules.
Frequently Asked Pipe Engineering Questions
Is STD pipe always the same as Schedule 40?
No. They coincide over only part of the size range. From NPS 12 onward, STD and Schedule 40 can differ, so the actual tabulated wall designation should be checked.
Is XS always the same as Schedule 80?
No. XS coincides with Schedule 80 only through part of the size range. At larger sizes the designations diverge.
What is the difference between NPS and DN?
NPS and DN are nominal designation systems. They identify a pipe-size family; neither should automatically be interpreted as the measured OD or ID.
Does a higher schedule always mean a higher pressure rating?
A thicker wall generally increases pressure capability for the same material and design conditions, but allowable pressure cannot be determined from schedule alone. Code equations, temperature-dependent allowable stress, joint factors, corrosion allowance and other requirements must be considered.
What is ASTM A106 Grade B?
ASTM A106/A106M is a specification for seamless carbon-steel pipe for high-temperature service. Grade B is one of its commonly specified grades.
What is the difference between ASTM A106 and API 5L?
They are different specifications developed for different intended scopes. API 5L is a line-pipe specification, while ASTM A106 addresses seamless carbon-steel pipe for high-temperature service. Project/code requirements determine which is appropriate.
Can an EN material be substituted for an ASTM material?
Not automatically. Any substitution should be evaluated against the governing code, mechanical properties, chemistry, toughness, dimensions, certification and project/client requirements.
Engineering Disclaimer
This calculator is intended for preliminary reference, estimation and educational use. Values should be verified against the current edition of the governing standard, approved project specifications, manufacturer documentation and engineering design before procurement, fabrication, pressure testing or construction. Element Folio does not present this page as a replacement for licensed standards.