Steel Profile Weight per Metre: Formula and Tables
The weight per metre of any steel section follows one formula: cross-sectional area times density. This guide shows the calculation step by step, explains unit conversion from cm² to kg/m, why catalogue figures can differ slightly, and how to turn a member list into total tonnage.
One formula for every steel profile
Every hot-rolled beam, channel, angle and hollow section obeys the same rule: the mass of one metre of a profile equals its cross-sectional area multiplied by the density of steel. Written out:
G = A × ρ
Here G is the weight per metre, A is the cross-sectional area and ρ is the density of the material. For structural carbon steel the standard value is ρ = 7850 kg/m³, and it is the same for all common grades: going from S235 to S355 changes strength, not density. That is why one weight table serves every grade.
This relationship is also why section tables always list the area A right next to the weight G: one is simply the other in disguise. If you remember a single number about steel, make it 7850 kg/m³.
From cm² to kg/m: getting the units right
Section tables give the area in cm² but the weight in kg/m, and mixing these units is where most calculation errors come from. The clean derivation has two steps:
- Convert the area to square metres:
A [m²] = A [cm²] ÷ 10 000. - Multiply by the density:
G [kg/m] = A [m²] × 7850.
Fold the two steps together and you get the estimator's shortcut, worth memorising:
G [kg/m] = A [cm²] × 0.785
The factor 0.785 is nothing mysterious: it is just 7850 divided by 10 000, i.e. the density expressed per square centimetre of area and per metre of length. Two practical checks:
- If your source (a CAD model, for instance) reports the area in mm², divide by 100 first to get cm² before applying the shortcut.
- A quick sanity check: the result in kg/m should come out in the same order of magnitude as the area value in cm². If your result is off by a factor of a hundred, a unit slipped somewhere.
Why the catalogue weight differs from your calculation
Multiply a published area by 0.785 and you will often land close to the published weight, but not exactly on it. There are several honest reasons for the gap:
- Rounding. Catalogues round A and G independently, each to a few significant figures, so the two printed values are not perfectly consistent with each other.
- Idealised geometry. The tabulated area is computed from nominal dimensions, including idealised fillet and corner radii. The real rolled or formed shape deviates slightly.
- Rolling and forming tolerances. Standards such as EN 10034 (tolerances for structural I- and H-sections) and EN 10219 (cold-formed welded hollow sections) permit the delivered product to deviate from nominal dimensions and mass by a few per cent. A physical bar on the scale will rarely match the theoretical figure exactly.
- Coatings. Galvanising or shop paint adds mass that is never included in the tabulated G.
For design, estimating and invoicing, the convention is to use the nominal (theoretical) weight from the tables. Weighed (actual) mass matters mainly for shipping, crane picks and mill invoicing where the contract says so.
From kg/m to total tonnage
Once you trust the per-metre weight, total tonnage for a structure is bookkeeping:
- List every member with its profile and its length in metres.
- For each line, multiply the weight per metre by the length:
m = G × L. - Sum all lines and divide by 1000 to convert kilograms to tonnes.
For a realistic procurement figure, estimators then add allowances on top of the net (theoretical) tonnage:
- Offcuts and waste. Bars come in stock lengths, and nesting is never perfect.
- Connections and fittings. Plates, stiffeners, bolts and welds are usually covered by a percentage uplift on the member weight rather than counted piece by piece at the early stage.
Keep the net tonnage and the allowances as separate line items: the net figure feeds structural checks and comparisons between design options, while the grossed-up figure feeds the purchase order.
Quick lookup tables
For everyday work you rarely compute G by hand; you look it up. The tables below list the weight per metre and cross-sectional area for three widely used European families:
IPE beams (see the full family page at IPE profiles):
HEA beams (see the full family page at HEA profiles):
| Profile | G [kg/m] | A [cm²] |
|---|---|---|
| HEA 100 | 16.7 | 21.2 |
| HEA 120 | 19.9 | 25.3 |
| HEA 140 | 24.7 | 31.4 |
| HEA 160 | 30.4 | 38.8 |
| HEA 180 | 35.5 | 45.3 |
| HEA 200 | 42.3 | 53.8 |
| HEA 220 | 50.5 | 64.3 |
| HEA 240 | 60.3 | 76.8 |
| HEA 260 | 68.2 | 86.8 |
| HEA 280 | 76.4 | 97.3 |
| HEA 300 | 88.3 | 112.5 |
| HEA 320 | 97.6 | 124.4 |
| HEA 340 | 104.8 | 133.5 |
| HEA 360 | 112.1 | 142.8 |
| HEA 400 | 124.8 | 159.0 |
| HEA 450 | 139.8 | 178.0 |
| HEA 500 | 155.1 | 197.5 |
| HEA 550 | 166.2 | 211.8 |
| HEA 600 | 177.8 | 226.5 |
| HEA 650 | 189.7 | 241.6 |
| HEA 700 | 204.5 | 260.5 |
| HEA 800 | 224.4 | 285.8 |
| HEA 900 | 251.6 | 320.5 |
| HEA 1000 | 272.3 | 346.9 |
UPE channels (see the full family page at UPE profiles):
The same data, plus section moduli and moments of inertia, is available for the other families too: HEB and HEM heavy beams, IPN and UPN tapered-flange sections, equal angles and unequal angles, and the hollow sections SHS, RHS and CHS.
Tip: export the tables to CSV
Every family page on this site lets you export the whole table as CSV. For tonnage take-offs this beats retyping: download the family table, paste it into a spreadsheet next to your member list, look up G per profile with a lookup function, multiply by the length column and sum. When the design changes profile sizes, only the lookup changes; the arithmetic stays put.
The CSV also makes the consistency check from this article trivial: add a helper column computing A × 0.785 and compare it with the published G, a quick way to convince yourself, and your colleagues, that the formula and the tables tell the same story.