Structural Steel & Lumber Weight Calculator
Estimate the weight of a structural steel member or a piece of lumber from its profile, dimensions and length. Choose a steel section — flat bar, square or round bar, round or square tube, angle, channel, I-beam or H-beam — or a nominal lumber size, and the calculator works out the cross-sectional area, then multiplies by length and a reference density. The densities are configurable and clearly labelled, since steel varies by grade and timber varies widely by species and moisture. Nominal lumber sizes are larger than the actual dressed dimensions, which the tool accounts for.
How to use this tool
- Choose structural steel or lumber.
- For steel, pick the profile and enter its dimensions in millimetres; for lumber, pick the nominal size.
- Enter the length in metres.
- Choose or accept the reference density for the material.
- Read the cross-sectional area, weight per metre and total weight.
The formula
The weight of a straight structural member is its cross-sectional area times its length times the material’s density. The area comes from the profile geometry; the density is a labelled reference value.
weight = area × length × density
e.g. flat bar area = width × thickness- area
- Metal cross-section (not bounding box)
- density
- Steel ≈ 7850 kg/m³ (reference)
Steel density varies slightly by grade and lumber density varies widely by species and moisture, so results are estimates. Nominal lumber sizes are larger than the actual dressed dimensions.
Worked examples
Steel flat bar
- Given
- 50 × 10 mm, 6 m
- Result
- ≈ 23.6 kg
Area 500 mm² = 5×10⁻⁴ m², times 6 m times 7850 kg/m³ gives about 23.6 kg.
Round tube
- Given
- 50 mm OD, 3 mm wall, 6 m
- Result
- ≈ 20.9 kg
The tube’s ring area times length times steel density; the hollow centre saves weight over a solid bar.
Timber joist
- Given
- 2×6 softwood, 3 m
- Result
- ≈ 8 kg
A nominal 2×6 is actually 1.5″ × 5.5″; at 500 kg/m³ over 3 m it is roughly 8 kg — though moisture can change this a lot.
Frequently asked questions
By multiplying the cross-sectional area of the profile by its length and by the material’s density. The area comes from the shape’s geometry — for a tube, the ring area; for an I-beam, the flanges plus web. That gives volume, and volume times density gives mass.
Lumber is named by its rough-sawn nominal size, then planed smooth to a smaller finished dimension. A “2×4” starts at 2 by 4 inches but ends up about 1.5 by 3.5 inches. The calculator uses the actual dressed dimensions, which is what determines the real weight.
Close, but treat it as an estimate. It uses the ideal cross-section and a reference density of 7850 kg/m³. Real rolled sections have fillets and rounded corners that add a little material, and density varies slightly by grade. For precise figures, use the published section tables for the specific profile.
Because timber density depends heavily on species and moisture. A dry softwood might be 400 kg/m³, a dense hardwood 750, and freshly cut “green” timber far heavier because of its water content. The tool lets you choose the density, but a single value cannot capture every piece — weigh it if precision matters.
Yes. The steel side lets you pick aluminium, brass or copper densities, so the same profile geometry gives the weight in those materials. Aluminium at about a third of steel’s density is a common comparison when choosing between weight and strength.