SpecBase

NPS 4-1/2 (DN 115) pipe — dimensions and weight

Outside diameter 127.0 mm (5 in), unchanged by schedule. This page lists all 7 tabulated schedules that fit on that diameter, with wall thickness, bore, mass per metre and internal volume.

Outside diameter
127.0mm
5 in · same in every schedule
Schedules tabulated
7
0.25–0.71 in wall
Sch 40 mass
18.679kg/m
12.552 lb/ft · 6.27 mm wall
Sch 40 bore
114.5mm
10.29 L/m internal volume
Mass range
18.7–48.5 kg/m
thinnest to heaviest tabulated wall
NPS 4-1/2 does not measure 4-1/2 inches anywhere

Nominal pipe size is a label, not a dimension. The outside diameter of NPS 4-1/2 is 5 in (127.0 mm), and the bore depends entirely on the wall you choose — 114.5 mm on the thinnest tabulated wall down to 90.9 mm on the heaviest. The naming convention was fixed decades ago so that a fitting size could serve every wall thickness; it is not a measurement, and treating it as one is how a line gets sized off a table for the wrong pipe.

NPS 4-1/2 (DN 115) — every tabulated schedule

NPS 4-1/2 (DN 115) — all schedules
Schedule Wall mm Inside dia. mm Metal area mm² Mass / length Water capacity L/m
40S 6.27 114.5 2,379.5 18.679 kg/m · 12.552 lb/ft 10.288
40 6.27 114.5 2,379.5 18.679 kg/m · 12.552 lb/ft 10.288
STD 6.27 114.5 2,379.5 18.679 kg/m · 12.552 lb/ft 10.288
80S 9.02 109.0 3,342.2 26.236 kg/m · 17.630 lb/ft 9.325
80 9.02 109.0 3,342.2 26.236 kg/m · 17.630 lb/ft 9.325
XS 9.02 109.0 3,342.2 26.236 kg/m · 17.630 lb/ft 9.325
XXS 18.03 90.9 6,173.5 48.462 kg/m · 32.565 lb/ft 6.494

Wall thicknesses derived from ASME B36.10M / B36.19M. Outside diameter 127.0 mm. Mass computed for Carbon Steel at 7850 kg/m³.

STD and XS are derived rather than tabulated: STD equals Sch 40 up to NPS 10 and is fixed at 0.375 in above it; XS equals Sch 80 up to NPS 8 and is fixed at 0.500 in above. Both appear here as separate rows because both are orderable designations.

How NPS 4-1/2 pipe weight is calculated

Sch 40 at this size, step by step

m = π/4 · (D² − d²) · 10⁻⁶ · ρ

D is outside diameter, d is bore (D − 2t), ρ is density in kg/m³, m is mass in kg per metre.

Worked through with the default dimensions:

D = 127.0 mm (5 in, fixed for every schedule)t = 6.27 mm (Sch 40)d = D − 2t = 127.0 − 12.55 = 114.5 mmA = π/4 × (127.0² − 114.5²) = 2,379.5 mm²m = 2,379.5 × 10⁻⁶ × 7,850 = 18.679 kg/m (12.552 lb/ft)
D
127.0 mm — fixed by the standard for NPS 4-1/2
t
6.27 mm for Schedule 40 at this size
d
114.5 mm — the bore, and the dimension that governs flow
ρ
7,850 kg/m³ for carbon steel

Internal volume and surface area

Mass is only one of the quantities that fall out of the same geometry. Two others decide real work on a line, and neither appears on a printed pipe chart:

Per metre of NPS 4-1/2 pipe, across the tabulated wall range
Wall vs range Wallmm Boremm Masskg/m
25 % 0.36 126.3 1.13
50 % 0.48 126.0 1.49
100 % 0.71 125.6 2.21
200 % 1.17 124.7 3.64
500 % 2.56 121.9 7.86
1,000 % 4.88 117.2 14.69

Sampled across the lightest to heaviest tabulated wall at this size. Mass rises roughly linearly with wall while the bore falls, which is the trade-off a schedule choice actually represents.

  • Internal volume — 10.288 L/m in Sch 40 ( 2.718 US gal/ft). Multiply by the line length to size a hydrostatic test or a flush.
  • External surface — 0.3990 m² per metre of pipe, which is what a coating or insulation quantity is priced against. It depends only on the outside diameter, so it is identical in every schedule at NPS 4-1/2.
  • Water mass — 10.29 kg per metre of water at 1,000 kg/m³. This is the number that decides whether a support is adequate during a test, not in service.

Download this size

NPS 4-1/2 pipe — CSV

Exports the schedule table above. The full pipe dataset, every size against every schedule, is on the downloads page.

All pipe data (CSV · 31 sizes)

Frequently asked questions

What is the outside diameter of NPS 4-1/2 pipe?

NPS 4-1/2 pipe has an outside diameter of 127.0 mm (5 in), and that diameter is fixed for every schedule at this size. Nominal pipe size is a label, not a dimension: NPS 4-1/2 does not measure 4-1/2 inches anywhere. The naming convention was chosen so that the outside diameter stays constant while the wall varies.

How much does NPS 4-1/2 pipe weigh?

In Schedule 40 it weighs 18.679 kg/m (12.552 lb/ft) with a 6.27 mm wall and a 114.5 mm bore. The heaviest tabulated wall for this size (XXS at 18.03 mm) gives roughly 48.5 kg/m — several times the Sch 40 figure.

How many schedules are available for NPS 4-1/2?

This page lists 7 tabulated schedules, including the derived STD and XS walls. Note that STD and Sch 40 are the same thickness at the small sizes and different from NPS 12 upward, and XS and Sch 80 are the same up to NPS 8 and different above — the two confusions that most often produce a wrong order.

What is the internal diameter of NPS 4-1/2 pipe?

The bore is the outside diameter minus twice the wall thickness. The table above gives it for every tabulated schedule at this size.

Nearby nominal sizes

Adjacent sizes in the NPS series. Outside diameters step non-uniformly — the jump from NPS 14 to NPS 16 is 2 in, the same as from NPS 2 to NPS 4.

Schedules at this size

Each schedule page lists every size that carries that wall.

Pipe reference and tools

Data source and method

Outside diameter for NPS 4-1/2 is the standard's governed value of 5 in, converted at exactly 25.4 mm per inch. Wall thicknesses are the tabulated B36.10M / B36.19M values. Mass, bore, internal volume and surface areas are computed on this page.

  • ASME B36.10M — Welded and Seamless Wrought Steel Pipe (dimensional tables).
  • ASME B36.19M — Stainless Steel Pipe (dimensional tables).
  • BIPM / NIST definitional constants: international inch = 25.4 mm, foot = 0.3048 m, pound = 0.45359237 kg.

Dataset version 2026.09.1 · dimensions last verified against source 2026-09-21. Found an error? Report it — corrections are issued with a version bump.