XXS pipe — dimensions and weight

14 sizes carry a tabulated XXS wall, from NPS 1/2 (21.3 mm OD) to NPS 8 (219.1 mm OD). Weights are computed at 7,850 kg/m³ for carbon steel, so a carbon-steel figure here runs about 0.1 % heavier than a mill chart calculated at a rounded nominal density.

How XXS pipe weight is calculated

A pipe is an annulus, so the metal area is the full circle less the bore:

Mass per unit length

m = π/4 · (D² − d²) · 10⁻⁶ · ρ, d = D − 2t

D is the outside diameter, t the wall thickness, d the resulting bore, ρ the material density in kg/m³ and m the mass in kg per metre of length.

Worked through with the default dimensions:

D = 6.625 in × 25.4 = 168.3 mmt = 0.864 in × 25.4 = 21.95 mmd = D − 2t = 168.3 − 2 × 21.95 = 124.4 mmA = π/4 × (168.3² − 124.4²) = 10,088.6 mm²m = 10,088.6 mm² × 10⁻⁶ × 7,850 kg/m³ = 79.195 kg/m

D

Outside diameter — governed by the standard, constant across schedules at a given NPS

t

Wall thickness — this is what the schedule designates, 7.47–22.22 mm across the sizes here

d

Inside diameter, D − 2t. Flow capacity follows this, not the nominal size

ρ

Density, 7,850 kg/m³ for carbon steel

Two consequences worth keeping in mind. First, because the outer diameter is fixed by the standard and the schedule only moves the wall inward, a heavier schedule costs bore rather than gaining outside diameter — the pipe still fits the same fitting, it just carries less. Second, the metal is a small fraction of the whole: at NPS 6 XXS the steel is 45.4 % of the full circle's area, which is why pipe is priced and handled as a hollow product rather than as bar stock.

XXS — complete size table

Outside diameters and wall thicknesses derived from ASME B36.10M / B36.19M. Mass computed at 7850 kg/m³ (Carbon Steel).

Sizes marked with a stainless schedule come from ASME B36.19M and the rest from B36.10M; where the standard groups two schedules in one column (Sch 10S/10 at the small end) both keys carry the same wall so a lookup never has to know about the grouping.

XXS against every other schedule at NPS 6

A single nominal size is the clearest place to see what a schedule actually changes. The outside diameter is the same in every row; only the wall moves.

Wall thicknesses derived from ASME B36.10M / B36.19M. Outside diameter 168.3 mm. Mass computed for Carbon Steel at 7850 kg/m³.

Dimensions and mass, in separately addressable form

The water capacity column above is the internal volume per metre — the figure that sizes a hydrostatic test. It is the clearest illustration of why bore matters more than nominal size: two pipes both sold as NPS 6 can differ by a factor of several in the volume they hold.

V = π/4 · d² × 10⁻⁶ L/m at d in mm — for NPS 6 XXS, d = 124.4 mm gives 12.15 L/m, or 12.15 kg of water per metre.

Download this schedule

Frequently asked questions