ms rectangular pipe weight calculator

What you can use this calculator for

Rectangular MS pipes are used for frames, gates, structural members, conveyor supports, racks, and general fabrication. Fabricators often need a quick weight for quoting, lifting plans, or checking shipping class. This page gives a theoretical mass from the geometry you type—not a mill test certificate.

Rectangular hollow sections in practice

In workshops and on site, rectangular hollow sections (RHS) are popular because they offer high bending stiffness about the major axis, flat faces that are easy to bolt or weld to, and predictable member lengths for portal frames, mezzanine posts, machine bases, trailer and body framing, hoarding posts, and solar or signage structures. Knowing mass per metre helps you compare profiles in a bill of materials, estimate paint or galvanizing area (outer perimeter × length as a first pass), and sanity-check supplier quotations when only dimensions and thickness are listed.

Structural design still requires section classification, connections, buckling checks, and code-compliant material grades; mass alone never proves adequacy. Treat any online estimate as complementary to drawings, standards, and engineer sign-off where those apply.

Formula in plain steps

1. Measure or read from a catalogue the outside width B and outside height H of the rectangle (both in mm in this tool).
2. Enter wall thickness t in mm. The model assumes the same wall all around, so the inner cavity measures (B − 2t) by (H − 2t).
3. Cross-sectional steel area: A = B·H − (B − 2t)(H − 2t) in mm².
4. Convert to m²: A_m² = A_mm² / 1 000 000.
5. Steel volume for length L (metres): V = A_m² × L.
6. Mass: m = ρ × V with mild steel often ρ ≈ 7850 kg/m³ unless your supplier specifies otherwise.

Worked example (you can verify in a spreadsheet)

Take a tube with outer 100 mm × 50 mm, wall 3 mm, length 6 m, and mild steel ρ = 7850 kg/m³:

• Inner cavity: (100 − 6) × (50 − 6) = 94 × 44 = 4 136 mm².
• Outer rectangle: 100 × 50 = 5 000 mm²; steel area = 5 000 − 4 136 = 864 mm² (same as 2t(B + H − 2t) = 6 × 144).
• Area in m²: 864 / 1 000 000 = 0.000 864 m².
• Volume over 6 m: 0.000 864 × 6 ≈ 0.005 184 m³.
• Mass: 0.005 184 × 7850 ≈ 40.7 kg; mass per metre ≈ 6.78 kg/m.

Enter the same numbers in the form above—the results should match within rounding of the display format.

Catalogues, standards, and how tubes are made

Most structural RHS on the market is electric-resistance welded (ERW): flat strip is formed into an open section and welded along the seam, then shaped to final rectangular dimensions. Seamless rectangular tube is less common and usually more expensive; the same area formula still models the steel envelope if walls are reasonably uniform. Regional standards (for example hollow-section standards used in India, Europe, or North America) define tolerances on side dimensions, squareness, twist, and sometimes mass per metre; always use the schedule that matches your procurement specification when arguments about acceptance arise.

If your drawing lists inside dimensions instead of outside, convert to outside first by adding twice the nominal wall to each inner side—or measure the piece directly on unused stock before cutting.

Typical densities when you change the material field

The math is always mass = density × volume. Mild carbon steel is often taken near 7850 kg/m³; stainless austenitic grades are frequently quoted in a similar band (roughly 7 900–8 000 kg/m³ depending on nickel and chromium); aluminium alloys are near 2 700 kg/m³. Hollow aluminium profiles use the same hollow-rectangle area method—only ρ changes.

From kg to freight, paint, and yard handling

Once you have kg/m or total kg, you can scale to bundles: multiply by number of identical lengths, then add a small allowance for dunnage, strapping, and handling fixtures. For road or container loading, compare against axle and payload limits using your total shipment mass—not individual sticks in isolation. Paint and hot-dip galvanizing budgets sometimes start from surface area; a quick outer perimeter estimate is 2(B + H) in mm per metre of length (plus inner perimeter if you need both sides coated).

For payment disputes or high-value orders, a weighbridge ticket on a sampled bundle beats any geometric estimate. Use the calculator for speed; use scales when money or custody transfer depends on the last kilogram.

Square hollow sections and round tubes (mental model)

A square hollow section (SHS) is just RHS with B = H; the same formula applies. A round pipe is different geometry (annulus π/4 × (D_outer² − D_inner²)); do not plug a round outer diameter into the rectangular fields. If you are comparing a round alternative to an RHS member, run two separate calculations with the correct shape for each.

Pros and cons of this approach

Things to keep in mind

• Measure carefully: use a straight, undamaged length; dents or bends change the true cross-section compared with catalogue nominal sizes.
• Mill tolerances: real B, H, and t can sit within allowed bands around the nominal print—small dimensional drift changes mass slightly but can add up on long runs.
• Project vs stick weight: mitres, cope cuts, weld metal, and offcuts mean the steel you buy or handle on site is often more than the sum of ideal calculator lengths for finished members.
• Lifting and transport: treat any computed kg as a planning number only; rigging, dynamic factors, and code rules need a qualified engineer or rigger for real picks and loads.
• Coatings and attachments: paint, powder coat, labels, clips, and internal stiffeners are not in the hollow-steel formula—add allowances separately when they matter.
• Stay in one unit system: the fields on this page expect outer dimensions and thickness in millimetres and length in metres; mixing cm or feet without converting is a common source of large errors.

Frequently asked questions

Glossary

RHS

Rectangular hollow section—a steel tube with a rectangular cross-section.

MS

Mild steel: low-carbon steel commonly used for structural hollow sections.

Nominal vs measured size

Catalogues often list nominal B, H, and t; real extrusions or rolled sections can deviate within tolerance bands.

ERW

Electric-resistance welded tube: strip formed and welded along a longitudinal seam, then sized to finished hollow dimensions.

kg/m

Kilograms per metre of member length—useful for scaling stock lists and comparing profiles of different lengths.

Theoretical mass

Mass from geometry and density alone, before weighbridge verification or tolerance effects.