Free · Calculator 9
Unit converter for piping
DN and NPS with the outside diameters of the EN, ASME, hygienic and plastic series, schedules and wall thicknesses, PN and Class with pressure-temperature rating, material numbers with ASTM equivalent.
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Basis & sources
What the tool calculates with, which standards and data it relies on and where its limits are. As of September 2026. For practice: Understand it and try it out.
Calculation method
- DN ↔ NPSMapping with the outside diameters per standard
- ScheduleWall thicknesses per ASME B36.10/B36.19
- PN ↔ ClassRating per material group and temperature
- MaterialsNumber, short name, comparable ASTM material
Standards & codes
Reference: the assistant follows Autodesk's file structure and the connection types of these standards. Standard texts and standard tables are not included.
| EN 10220 / DIN EN ISO 1127 | Outside diameter EN |
|---|---|
| ASME B36.10 / B36.19 | Schedules and wall thicknesses |
| ASME B16.5 | Pressure-temperature ratings per material group |
| DIN EN 1092-1 | PN flanges |
Data & origin
| All tables | from the Piping Spec Calculator (one source per value) – estimates from publicly available manufacturer data, generalized |
|---|---|
| Material equivalents | comparable, not identical – guide values |
Assumptions & limits
- EN and ASTM materials differ in strength, testing scope and approval – substitute only after checking.
- Class flanges with PN designation: bolt circles differ; the rating is decisive.
Standards status for this page 5 standards · researched September 2026
| Standard | Contents | Current edition | Replaced / successor |
|---|---|---|---|
| ASME B36.10 (until 2018: B36.10M) | Welded and Seamless Wrought Steel Pipe | ASME B36.10-2022 | replaces ASME B36.10M-2018 |
| DIN EN 10220 | Seamless and welded steel tubes – General tables of dimensions and masses per unit length | DIN EN 10220:2003-03 | replaces DIN V ENV 10220:1994-02; DIN 2448:1981-02; DIN 2458:1981-02 |
| DIN EN ISO 1127 | Stainless steel tubes – Dimensions, tolerances and conventional masses per unit length | DIN EN ISO 1127:2019-03 | replaces DIN EN ISO 1127:1997-03 |
| ASME B16.5 | Pipe Flanges and Flanged Fittings NPS 1/2 through NPS 24 Metric/Inch | ASME B16.5-2025 | replaces ASME B16.5-2020 |
| DIN EN 1092-1 | Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN designated – Part 1: Steel flanges | DIN EN 1092-1:2018-12 | replaces DIN EN 1092-1:2013-04; DIN EN 1092-1 Corrigendum 1:2014-08 |
Researched at DIN Media, ISO, IEC and ASME, as of September 2026. Before binding use, please check the current edition with the standards publisher. Overview of all standards: Plant Engineering Infobase · Standards status.
Understand it and try it out
European and American standards name the same things differently. If you read a third-party specification, you need to be able to translate – otherwise pipe and flange will not fit together.
The terms in five minutes
- DN (nominal size)
- A designation, not a dimension. DN 100 has an outside diameter of 114.3 mm, not 100 mm.
- NPS (Nominal Pipe Size)
- The American designation in inches. From NPS 14, NPS equals the outside diameter in inches; below that, it does not.
- Outside diameter series
- EN (ISO) and ASME have the same outside diameter for many sizes, but not for all: DN 65 is 76.1 mm in EN and 73.0 mm in ASME.
- Schedule (Sch)
- Wall thickness class in ASME. Sch 40 is a different wall thickness for every size; up to NPS 10, Sch 40 = STD.
- PN (nominal pressure)
- Pressure rating in Europe, roughly the permissible pressure in bar at room temperature. As the temperature rises, the permissible pressure decreases.
- Class (pressure class)
- Pressure class for ASME flanges (150, 300, 600 …). The permissible pressure depends on material group and temperature (rating table), not on the number.
- Material number
- 1.xxxx per EN 10027-2, e.g. 1.4404; the short name describes the composition (X2CrNiMo17-12-2). ASTM equivalents are comparable, not identical.
Try it out and understand it
Change one value in the calculator above and watch what happens to the others:
| Try it | What happens | Why |
|---|---|---|
| Look up DN 65 in both series | EN 76.1 mm, ASME 73.0 mm. | An ASME DN 65 fitting does not fit an EN DN 65 pipe – a classic in mixed projects. |
| Compare Schedule 40 at NPS 2 and NPS 12 | The wall thickness is completely different. | Schedule is a class, not a fixed wall thickness. |
| Look at Class 150 at 20 °C and 200 °C | The permissible pressure drops considerably. | The strength of the material decreases with temperature – that is why there are rating tables. |
Typical mistakes
- Confusing Class 150 with PN 150 – depending on temperature, Class 150 is more like 20 bar or below.
- Assuming that PN flanges and Class flanges fit together – bolt circles and facings differ.
- Treating ASTM and EN materials as identical – for verification, the material actually ordered is what counts.
For practice
Exercise: an American specification says "NPS 4, Sch 40, Class 300, A312 TP316L". What does that mean in European (EN) terms?
Show solution
NPS 4 ≈ DN 100 with an outside diameter of 114.3 mm; Sch 40 means 6.02 mm wall thickness at this size; Class 300 is the pressure class of the flanges (permissible pressure from the rating table for the material group); A312 TP316L is a seamless or welded stainless steel pipe, comparable to 1.4404. In the converter: open the DN ↔ NPS, Schedule, PN ↔ Class and Materials tabs one after the other.
For training and studies: this page may be shown in class. Property values are guide values; for verification, the standards and manufacturer data apply.
What is the calculator for?
Why you need it
In international projects, EN and ASME standards meet. The same nominal size does not mean the same diameter, Class flanges do not fit PN flanges, and the same material has a different name depending on the standard.
Which tasks it solves
- What is the outside diameter of NPS 2½ – and does DN 65 match it?
- Which schedule corresponds to a 6 mm wall thickness?
- Which Class do I need for 25 bar at 200 °C?
- Which ASTM material is comparable to 1.4404?
When in the design process
- Basics / preliminary designCompare the customer specification with your own standard
- Basic engineeringCreate piping specs, read in third-party specs
- Detail engineeringTranslate bills of materials and orders
- Installation / commissioning–
- Operation / modification of existing plantsSpare parts for existing plants built to another standard
What matters
Same DN, different diameter
DN 65 is 76.1 mm in EN and 73.0 mm in ASME – fittings and flanges do not fit together.
Class is not PN
The PN designation of Class flanges is just a name. Bolt circles differ; the rating of the material group is decisive.
Comparable is not identical
EN and ASTM materials differ in strength, testing scope and approval – substitute only after checking.
Preliminary sizing for design work – not a verification. Dimensions and material properties come from the ASEING Piping Spec Calculator and Support Span Calculator and are estimates from publicly available manufacturer data, generalized; all other values are guide values. They may deviate from the standard – check against the applicable standards and manufacturer data before binding use. You can enter your own values in the calculator.