Weights and lifting
Steel member and schedule weight from section mass per metre
- where
- total weight with fittings (kg)
- section mass per metre (kg/m)
- length of each member (m)
- number of members
- fittings allowance (%)
- total weight (t)
Explain this equation
Works out the total weight of a batch of identical steel members from the mass per metre in the section size. Use it for tonnage schedules, delivery loads and as a first step towards lift weights.
w is the mass of one metre of the bare section, the last figure in a UK serial size. L is the length of each member and n is how many there are. f_a adds the end plates, cleats, stiffeners and bolts as a percentage of the bare steel. M_t is the same total in tonnes.
Weight scales directly with length and number, so the equation is a straight product. The bracket turns the percentage allowance into a multiplier: 5% becomes 1.05. Dividing by 1000 converts kilograms to tonnes.
Sense check: twelve 8 m lengths of 67 kg/m beam are about 6.4 t bare, and about 6.8 t with a 5% allowance. Doubling the length doubles the weight.
Watch out: the fittings allowance is your estimate, not a standard figure. For lifting, use the fabricator’s marked piece weight when you have it.
Weight of a run of identical members from the serial size mass per metre, with an allowance for the fittings welded or bolted to them. Use it for tonnage schedules, delivery loads and as the starting point for lift weights.
Enter your values to see the result.
Good to know
The last number in a UK serial size is the nominal mass in kg/m (457 × 191 × 67 UKB is 67.1 kg/m), worked out at 7850 kg/m³. The fittings allowance covers end plates, cleats, stiffeners, splice plates and bolts. There is no standard figure: take it from the fabrication drawings or your own records for similar frames. Simple beams with end plates may add only a few per cent; heavily detailed members much more.
Common mistake
Using the nominal serial size instead of the exact mass per metre, or forgetting fittings, which can understate the piece weight used for lifting.
Limits
Straight prismatic members of one section. For lift planning use the fabricator’s piece weight from the drawing where available.
Sources
- SCI / Steel for Life Blue Book: section dimensions and properties (533 × 210 × 82 UKB: h 528.3, b 208.8, tw 9.6, tf 13.2, r 12.7 mm, A 105 cm²)
- BS EN 1993-1-1 Eurocode 3: Design of steel structures – General rules (3.2.6: α = 12 × 10⁻⁶ per K, density 7850 kg/m³)
- BCSA National Structural Steelwork Specification for Building Construction, 7th edition, 1st revision (2023) – Section 9 accuracy of erected steelwork; Section 7 cambers; 8.6.2 reference temperature 20 °C
Results are calculations from the published methods and figures shown, and depend on the data you enter. Always work to the engineer’s drawings and bending schedules, BS 8666, BS EN 1992, BS EN 1090-2, BS 5531/the BCSA National Structural Steelwork Specification and manufacturers’ data. Lifting must be planned under LOLER by a competent person.