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The pipe's outer diameter.
The outside diameter, which for nominal-bore pipe is NOT the nominal size: 2 in nominal pipe is 60.3 mm outside, and 4 in is 114.3 mm. Nominal bore is a naming convention that stopped matching the bore a century ago and never matched the outside. Read the actual outside diameter from a pipe table or measure it — a nominal figure typed in here is wrong by a fixed amount that grows with size.
The pipe's nominal wall thickness.
The wall for the schedule you are buying, not for the nominal size — the same nominal bore comes in several schedules and the wall is what separates them. Schedule 40 and schedule 80 at the same nominal size share an outside diameter and differ substantially in wall, which is the whole point of the schedule system and the reason weight cannot be derived from the size alone.
Weight per unit length
11.36 lb/ft
- Cross-sectional area
- 3.34 in²
They open the calculator with your figures already in it
Round Steel Pipe Weight Calculator: 11.36 lb/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Pipe cross-sectional area = π×(OD² − ID²)/4, where ID = OD − 2×wall thickness; weight per unit length = area × steel density (7850 kg/m³)
Inputs used
- Outer Diameter
- 4.5 in
- Wall Thickness
- 0.25 in
Intermediate steps
- Cross-sectional area
- 3.34 in²
What this calculation does not cover
- The outer diameter asked for is the pipe's measured outside diameter, not its nominal size, and the two only coincide from about 14 inches upward. Entering 101.6 mm for NPS 4 pipe, whose true outside diameter is 114.3 mm, returns 14.15 kg/m in place of 16.03 kg/m, roughly 12 per cent light, and nothing on the page can catch the substitution because 101.6 mm with a 6 mm wall is itself a perfectly valid pipe.
- The wall thickness is taken as nominal and used exactly as typed. Pipe specifications commonly permit a minus tolerance on wall, around 12.5 per cent for seamless product, so a 114.3 mm by 6 mm pipe rolled at the bottom of that tolerance weighs about 14.1 kg/m rather than 16.0. There is no corrosion allowance field either, so the figure describes the pipe as bought and not the wall left after service.
- Only the steel is weighed. The bore of a 114.3 mm by 6 mm pipe holds about 8.2 kg (18 lb) of water per metre, more than half the weight of the steel around it, and insulation, lining, external coating, flanges, valves and the water left in a line after a hydrostatic test all sit outside the number.
- This is a mass, not a capacity. Nothing here checks the pressure the wall can hold, the spacing at which the pipe may be supported, the span at which it deflects, or the stress in it during a lift. Two pipes of identical outside diameter and wall weigh the same whether they are a plain carbon grade or a high-strength line pipe grade, while their allowable pressures can differ by a factor of two.
- Density is fixed at 7,850 kg/m³ (490 pcf) and there is no material input. A stainless pipe of the same dimensions is about 1.9 per cent heavier at roughly 8,000 kg/m³ (499 pcf), and an aluminium one about a third of the figure shown, so a material substitution needs a different density.
Add the equipment this sizes
This result is a specification — 11.36 lb/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Pipe cross-sectional area = π×(OD² − ID²)/4, where ID = OD − 2×wall thickness; weight per unit length = area × steel density (7850 kg/m³)
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