Pipe, flange and fitting specifications

What PipeData is

PipeData is a free reference for the dimensions of steel pipe, flanges and buttweld fittings made to the ASME B36 and B16 standards. It is written for the people who look these figures up during a working day: piping designers and drafters checking a drawing, pipefitters and welders on a fabrication floor, buyers and estimators preparing an enquiry, inspectors identifying what is in front of them, and students learning how piping is specified.

A table of numbers only helps if you know what the numbers mean, so the site pairs every table with an explanation. Pipe size pages say what each schedule does to the bore, the weight and the pressure the pipe will hold. Flange pages say what a pressure class is rated for and where each flange type is used. The guides work through the calculations behind a size or a schedule, and the comparisons set two options side by side.

How to use the data

Three rules explain most of what is on this site, and most mistakes made with piping tables come from forgetting one of them.

1. The outside diameter belongs to the size. NPS 4 pipe is 4.500 in (114.3 mm) across in every schedule. Schedule 40 has a 0.237 in (6.0 mm) wall and Schedule 80 a 0.337 in (8.6 mm) wall, and the difference comes out of the bore, which goes from 4.026 in (102.3 mm) to 3.826 in (97.2 mm). Start on the pipe size pages.
2. A flange is sized by NPS and pressure class. An NPS 4 Class 150 flange is 9.00 in (228.6 mm) across with 8 bolts; in Class 300 it is 10.00 in (254.0 mm) across with 8 bolts. The class is not a pressure: in A105 carbon steel those two are rated 285 and 740 psig at 100 °F, and less when hot. Start on the flange pages and the rating tables.
3. A buttweld fitting is sized by NPS alone. An elbow or a tee takes up the same space in every schedule, so a layout can be dimensioned before the wall is chosen. Start on the fitting pages.

Figures that come straight from a standard are shown as tabulated. Figures worked out from them, such as bore, weight, flow area and water content, carry the formula beside the table. Inches come first because the standards are written in them; millimetres, kilograms per metre and bar are shown alongside.

Guides

Worked methods for the decisions the tables cannot make for you.

All guides →

Comparisons

Two options, the published dimensions of both, and when to use each.

All comparisons →

Pipe dimensions

Outside diameter, wall thickness, bore, weight and flow area for every ASME B36.10M size from NPS 1/8 to NPS 36, across all fourteen schedules. Each size page also lists the flanges and fittings made for that size.

Flanges

Six ASME B16.5 flange types across seven pressure classes — outside diameter, thickness, bolt circle, bolt count and bolt size — plus the large-diameter B16.47 series above NPS 24.

Large diameter flanges, NPS 26–60 →

Buttweld fittings

Centre-to-end dimensions from ASME B16.9. These depend on nominal size alone, so a single table covers every schedule.

Reference tables

Conversion charts and whole-range tables, for when the question spans every size at once.

Common questions

Does pipe outside diameter change with schedule?

No. Outside diameter is fixed for a given NPS. A higher schedule thickens the wall inward and shrinks the bore, which is what allows one set of flanges and fittings to serve every schedule in a size.

Is a Class 150 flange rated for 150 psi?

No. In A105 carbon steel a Class 150 flange is rated 285 psig at 100 °F, falling to 140 psig at 600 °F. The class number is a designation, not a pressure.

Do buttweld fitting dimensions change with wall thickness?

No. ASME B16.9 sets fitting dimensions from nominal size alone, so a schedule 10 and a schedule 160 elbow of the same NPS occupy exactly the same space.

What units does PipeData use?

Imperial is primary throughout — inches, pounds per foot, psig — with the metric equivalent shown alongside in millimetres, kilograms per metre and bar.

Can I design or buy from these tables?

Use them to look a figure up, to check a drawing or to prepare an enquiry. Before anything is fabricated, purchased or signed off, confirm the figure against a current copy of the governing standard. The About page explains how the data is compiled and checked, and what that checking does not cover.