Steel Weight Calculator

Every steel weight calculation reduces to one physical identity:

W = ρ · A · L

where ρ is the material density (7850 kg/m³ for carbon steel), A is the cross-section area, and L is the length of the piece. Because ρ and A are constant along a prismatic member, the industry works with the unit weight in kg/m (or lb/ft) — multiply it by the length and the quantity of pieces and you have the shipping weight, the crane pick weight, or the tonnage for the quote:

Total weight = (kg/m) × length (m) × quantity

This calculator gives you the kg/m two different ways, and both matter:

• Catalog mode looks the profile up in a real rolling catalog (1320 sections: W/H beams, IPE, HEA/HEB, channels, angles, HSS tubes, cold-formed C/U). Catalog values are the nominal weights published by the mills — the number your supplier's table shows and the number the invoice is based on.
• Generic shape mode computes A from raw dimensions (plate, round bar, square bar, flat bar, hex bar, pipe, rectangular tube, angle) and applies ρ·A·L. Use it for anything cut from plate or for sections that are not in a catalog.

A subtle but important detail: computed weights use the exact sharp-corner geometry. Real hot-rolled sections have fillets and cold-formed tubes have corner radii, which is why a computed RHS can come out 1–2 % heavier than the catalog line for the same nominal size. When a catalog value exists, prefer it — that is what you will be charged for.

The density of carbon steel is standardized at 7850 kg/m³ (0.00785 kg/mm²·m, 490 lb/ft³, 78.5 kN/m³ as specific weight) — the value used by every structural code, including NBR 8800, AISC 360 and Eurocode 3. Alloying changes it surprisingly little for stainless, and dramatically for aluminum:

* The zinc layer adds mass on top of the base steel — for ordinary hot-dip coatings (≈ 275–600 g/m² per side) this is 1–6 % depending on plate thickness; the calculator lets you enter a custom density if your spec requires it.

Pick the material in the dropdown (or type a custom density) and every mode — including the catalog, which is scaled from its carbon-steel nominal — updates instantly. That is how you price a 304 stainless version of a carbon-steel design without redoing a single measurement.

The most-searched steel weight question is the ms plate weight (mild-steel plate). The formula is direct:

Plate weight (kg) = Length (m) × Width (m) × Thickness (mm) × 7.85

Equivalently, one square meter of MS plate weighs 7.85 kg per millimeter of thickness (kg/m² = 7.85 · t). Quick reference for common plate thicknesses:

Metric mill plates are rolled to the round metric thicknesses above — the inch fractions are the nearest imperial equivalents (exact would be 9.525, 12.7, 15.875 and 19.05 mm), which is why the ≈ matters on an invoice.

Example — the standard 2000 × 1000 × 9.5 mm sheet: 2.0 × 1.0 × 9.5 × 7.85 = 149.15 kg. Type W = 1000 mm, t = 9.5 mm, L = 2 m in the Generic shape → Plate tab and you will see exactly that number, already pre-loaded as the default.

All of these are the same ρ·A·L identity with the area expanded — the constants below are for carbon steel (ρ = 7850 kg/m³), dimensions in mm:

• Round bar: kg/m = 0.006165 · d² — the classic rebar shortcut d²/162.2. A 20 mm bar weighs 0.006165 × 400 = 2.466 kg/m.
• Square bar: kg/m = 0.00785 · s²
• Flat bar / plate strip: kg/m = 0.00785 · w · t
• Hex bar: kg/m = 0.006798 · AF² (AF = across flats)
• Pipe (CHS): kg/m = 0.02466 · t · (D − t) — the exact closed form of π/4 · (D² − d²) · ρ. A 4" sch 40 pipe (114.3 × 6.02) gives 0.02466 × 6.02 × 108.28 = 16.07 kg/m, matching ASME B36.10 tables.
• Rectangular tube (RHS): kg/m = 0.00785 · [h·b − (h−2t)(b−2t)] = 0.0157 · t · (h + b − 2t), sharp corners.
• Angle (L): kg/m = 0.00785 · t · (h + b − t)

For any other density multiply by ρ/7850. The Generic shape tab shows the live cross-section area and the formula being applied, so the number is always auditable — no black box.

Real jobs are never one bar. The Cut list tab is a miniature bill of materials: each line holds a description, a unit weight (kg/m), a length and a quantity. Add lines by hand, or push whatever is currently selected in the Catalog or Shape tab with one click — the kg/m carries over automatically.

• The running total in kg, metric tons and lb updates as you type — that is the tonnage for your freight quote and the pick weight for the crane plan.
• Enter an optional price per kg (R$, $, € or £) and every line and the grand total get an instant cost column. Steel is sold by weight; this turns the weight sheet into a budget sheet.
• Export CSV or PDF — free, no login. The CSV opens directly in Excel / Google Sheets with item, kg/m, length, quantity, weight and cost columns; the PDF is a print-ready sheet with header, the selected profile's cross-section sketch, per-line weights and the costed totals — ready to attach to a proposal.

Because the list persists while you switch tabs, the natural workflow is: search a profile → set length × qty → Add to cut list → repeat → export. Estimators do this all day; here it takes seconds and costs nothing.

Mills publish nominal unit weights rounded from the exact rolled geometry — W150x13 is defined as 13.0 kg/m even though its exact area × ρ gives a slightly different number. Fabricators, hauliers and inspectors all reference the nominal value, and mill invoices are settled on it (with rolling tolerances of roughly ±2.5 % under EN 10034 / ASTM A6).

Use the rule of thumb:

1. Buying or quoting a rolled section? Use the Catalog tab — nominal kg/m is the commercial truth.
2. Cutting from plate, machining a bar, or using a non-catalog size? Use the Generic shape tab — ρ·A·L is the physical truth.
3. Estimating a whole package? Mix both freely in the Cut list — each line remembers the kg/m you gave it.

If you need more than weight — section properties, code checks to NBR 8800 / AISC 360 / EC3, or a full 3D model — every profile in this catalog has a dedicated page with a complete calculation report, and the same catalog powers the free CalcSteel 3D editor.