Structural pipe shows up on almost every job: bollards, handrail posts, columns in canopies and carports, pipe braces, sign supports. Drawings call it out several ways (PIPE6STD, 6" STD PIPE, 6" SCH 40, 6"Ø XS), and the numbers in the callout are not the actual dimensions. A 6 in. pipe has a 6.625 in. outside diameter. This chart gives the real OD, wall, and weight for every structural pipe size, and explains where "Schedule 40" and "Standard" stop meaning the same thing.
How Pipe Sizes Work
Pipe is named by nominal pipe size (NPS) and a wall class.
- NPS is a size name, not a measurement. From NPS 14 up, the OD equals the NPS. Below that, the OD is larger than the name: NPS 6 is 6.625 in. OD, NPS 4 is 4.500 in., NPS 2 is 2.375 in.
- Wall class is either a weight class (STD, XS, XXS) or a schedule number (Sch 40, Sch 80, and others). Both come from ASME B36.10M, the standard for welded and seamless wrought steel pipe dimensions.
- AISC designations use the weight classes: PIPE6STD, PIPE6XS, PIPE6XXS. That's the form you'll see in the AISC Manual and in most structural drawings produced from it.
Every size in a given NPS has the same OD. Heavier walls make the inside diameter smaller; the outside stays the same. A PIPE6STD and a PIPE6XXS are both 6.625 in. OD.
Structural Pipe Chart: STD, XS, and XXS
This table covers all 51 pipe sections in the AISC catalog. OD and nominal wall thickness are from the AISC Shapes Database v15.0, which follows ASME B36.10M. Weights are from the AISC shapes catalog. A dash means AISC doesn't list that size in that wall class.
| NPS | OD (in) | STD wall (in) | STD (lb/ft) | XS wall (in) | XS (lb/ft) | XXS wall (in) | XXS (lb/ft) |
|---|---|---|---|---|---|---|---|
| 1/2 | 0.840 | 0.109 | 0.85 | 0.147 | 1.09 | — | — |
| 3/4 | 1.050 | 0.113 | 1.13 | 0.154 | 1.48 | — | — |
| 1 | 1.315 | 0.133 | 1.68 | 0.179 | 2.17 | — | — |
| 1-1/4 | 1.660 | 0.140 | 2.27 | 0.191 | 3 | — | — |
| 1-1/2 | 1.900 | 0.145 | 2.72 | 0.200 | 3.63 | — | — |
| 2 | 2.375 | 0.154 | 3.66 | 0.218 | 5.03 | 0.436 | 9.04 |
| 2-1/2 | 2.875 | 0.203 | 5.8 | 0.276 | 7.67 | 0.552 | 13.7 |
| 3 | 3.500 | 0.216 | 7.58 | 0.300 | 10.3 | 0.600 | 18.6 |
| 3-1/2 | 4.000 | 0.226 | 9.12 | 0.318 | 12.5 | — | — |
| 4 | 4.500 | 0.237 | 10.8 | 0.337 | 15 | 0.674 | 27.6 |
| 5 | 5.563 | 0.258 | 14.6 | 0.375 | 20.8 | 0.750 | 38.6 |
| 6 | 6.625 | 0.280 | 19.0 | 0.432 | 28.6 | 0.864 | 53.2 |
| 8 | 8.625 | 0.322 | 28.6 | 0.500 | 43.4 | 0.875 | 72.5 |
| 10 | 10.750 | 0.365 | 40.5 | 0.500 | 54.8 | 1.000 | 104 |
| 12 | 12.750 | 0.375 | 49.6 | 0.500 | 65.5 | 1.000 | 126 |
| 14 | 14.000 | 0.375 | 54.6 | 0.500 | 72.2 | — | — |
| 16 | 16.000 | 0.375 | 62.6 | 0.500 | 82.9 | — | — |
| 18 | 18.000 | 0.375 | 70.7 | 0.500 | 93.5 | — | — |
| 20 | 20.000 | 0.375 | 78.7 | 0.500 | 104 | — | — |
| 24 | 24.000 | 0.375 | 94.7 | 0.500 | 126 | — | — |
| 26 | 26.000 | 0.375 | 103 | 0.500 | 136 | — | — |
Every row passes the pipe weight formula within 2% (see below). The weights are based on the nominal wall. AISC also publishes a design wall thickness of 0.93 × nominal for calculating section properties, but that affects strength calculations, not what the pipe weighs.
Schedule 40 vs STD, Schedule 80 vs XS
For small and mid sizes, the two naming systems line up:
- Sch 40 = STD from NPS 1/2 through NPS 10
- Sch 80 = XS from NPS 1/2 through NPS 8
Above those sizes they split. STD stays at a 0.375 in. wall from NPS 12 up, and XS stays at 0.500 in. from NPS 10 up, while the schedule walls keep growing with diameter. This is where estimates go wrong: a drawing that says "12" SCH 40" is not a PIPE12STD.
Sch 40 and Sch 80 walls below are from ASME B36.10M (as reproduced in the Project Materials B36.10 chart). STD and XS walls are from the AISC Shapes Database. The Sch 40 and Sch 80 weights are calculated with the B36.10M plain-end formula, not taken from a catalog, so treat them as estimating values.
| NPS | OD (in) | STD wall | Sch 40 wall | XS wall | Sch 80 wall | Sch 40 calc. (lb/ft) | Sch 80 calc. (lb/ft) |
|---|---|---|---|---|---|---|---|
| 10 | 10.750 | 0.365 | 0.365 | 0.500 | 0.594 | 40.52 | 64.49 |
| 12 | 12.750 | 0.375 | 0.406 | 0.500 | 0.688 | 53.57 | 88.71 |
| 14 | 14.000 | 0.375 | 0.438 | 0.500 | 0.750 | 63.50 | 106.23 |
| 16 | 16.000 | 0.375 | 0.500 | 0.500 | 0.844 | 82.85 | 136.74 |
| 18 | 18.000 | 0.375 | 0.562 | 0.500 | 0.938 | 104.76 | 171.08 |
| 20 | 20.000 | 0.375 | 0.594 | 0.500 | 1.031 | 123.23 | 209.06 |
| 24 | 24.000 | 0.375 | 0.688 | 0.500 | 1.219 | 171.45 | 296.86 |
At NPS 12, the Sch 40 pipe is 53.57 lb/ft against 49.6 for STD, about 8% heavier. At NPS 24, Sch 40 is 171.45 lb/ft against 94.7 for STD, nearly double. If the drawing says Sch 40 or Sch 80 on a large pipe, price that wall, and ask the engineer if you suspect they meant STD.
The Pipe Weight Formula
ASME B36.10M gives plain-end weight as:
lb/ft = 10.69 × (OD − t) × t
with OD and wall t in inches. The constant 10.69 is π × 3.4028, where 3.4028 is the weight in lb/ft of one square inch of steel section one foot long.
Example, PIPE6STD: 10.69 × (6.625 − 0.280) × 0.280 = 10.69 × 6.345 × 0.280 = 18.99 lb/ft. The AISC Shapes Database lists 19.0.
Example, PIPE4XS: 10.69 × (4.500 − 0.337) × 0.337 = 15.0 lb/ft, matching the table.
The same approach works for any round tube, and the underlying 3.4028 rule is explained in our steel beam weight guide.
Pipe vs Round HSS
Round HSS (ASTM A500 or A1085) is named by its actual OD and wall, as in HSS6.625x0.280, and comes in many more wall thicknesses than pipe. Pipe (usually ASTM A53 Grade B, which the AISC Manual lists as the preferred pipe material) is named by NPS and wall class. At the same OD and wall they weigh almost the same, but the grades, availability, and specification differ, and they're not interchangeable without the engineer's approval. The full comparison with side-by-side charts is in pipe vs round HSS, and the rest of the HSS family is covered in our HSS sizes guide.
A quick way to tell them apart on drawings: a decimal OD (6.625, 4.500) or an "HSS" prefix means round HSS. A whole or fractional size with STD, XS, XXS, or SCH means pipe.
How Pipe Appears on Drawings
The same member can be written many ways. All of these are PIPE6STD for estimating:
- PIPE6STD
- 6" STD PIPE
- P6 STD
- 6"Ø STD
- 6" SCH 40 PIPE (same as STD at NPS 6)
And these are not the same as each other:
- 12" STD (0.375 in. wall, 49.6 lb/ft) vs 12" SCH 40 (0.406 in. wall, about 53.6 lb/ft)
- PIPE6STD (6.625 in. OD) vs HSS6.000x0.250 (6.000 in. OD)
"XH" or "X-STRONG" on older drawings means XS; "XXH" means XXS. If a drawing gives only "6" PIPE" with no wall, the general notes usually set a default. If they don't, it's a question for the engineer, not an assumption. The section shorthand guide and the abbreviations guide list more variants.
Estimating Notes for Pipe
Bollards. Usually a short pipe length, concrete-filled, sometimes with a cap and a base plate. The steel weight is small; the fill, cap, paint, and installation are most of the cost. Count them per each, then add the steel weight from the table.
Handrail and guardrail posts. Small pipe (1-1/4 and 1-1/2 in. are common) at a regular spacing. Rails are usually priced by the linear foot with posts, returns, and end caps counted separately. See our stairs and railings takeoff guide.
Pipe columns. Add the cap plate and base plate as separate plate items. A 6 in. pipe column 12 ft tall is 19.0 × 12 = 228 lb before plates.
Galvanizing. Pipe is often galvanized when it's outside. Galvanizers price by weight, and the vent and drain holes pipe needs for galvanizing are a detail step to account for.
Estimating only. The dimensions and weights here are for takeoffs and budgets. Wall selection and capacity belong to the engineer.
Steelflo reads pipe callouts in their common forms (PIPE6STD, 6" STD, SCH 40) off your drawings and lists them in the takeoff alongside the rest of the steel for you to review. See how it works.
Frequently Asked Questions
What is the outside diameter of 6 inch Schedule 40 pipe?
6 in. Schedule 40 pipe has an outside diameter of 6.625 in. and a wall thickness of 0.280 in. It's the same as PIPE6STD and weighs about 19.0 lb per foot per the AISC Shapes Database.
Is Schedule 40 the same as Standard wall?
Only through NPS 10. From NPS 12 up, Standard (STD) wall stays at 0.375 in. while Schedule 40 keeps getting thicker, so a 12 in. Sch 40 pipe has a 0.406 in. wall. Check the exact callout on large pipe.
Is Schedule 80 the same as XS?
Only through NPS 8. From NPS 10 up, XS stays at 0.500 in. while Schedule 80 gets thicker: 0.594 in. at NPS 10 and 0.688 in. at NPS 12.
How do I calculate steel pipe weight per foot?
Use lb/ft = 10.69 × (OD − wall) × wall, with both dimensions in inches. For 4 in. XS pipe (4.500 in. OD, 0.337 in. wall), that's 10.69 × 4.163 × 0.337 = 15.0 lb/ft.
What does XXS mean on a pipe callout?
XXS means double extra strong, the heaviest standard wall class. In the AISC catalog it is listed for NPS 2 through 12, except 3-1/2. PIPE6XXS has a 0.864 in. wall and weighs 53.2 lb per foot.