Contents
Overview
Working out steel beam weight
How much does a steel beam weigh? Multiply its mass per metre by its length. On UK beams the mass per metre is the last number of the size, so a 305 x 165 x 40 universal beam (UB) weighs about 40 kg a metre, and a 6 m length comes to about 240 kg before any fittings.
In short
- In the deepest UB sizes the heaviest version weighs more than twice the lightest, so read all three numbers of the size.
- A beam with no size on it can be measured and its weight worked out from its cross-section.
- Published section weights leave out fittings, so plates and bolts go on top.
- For a crane lift, the hook block (the hook and pulley block hanging from the crane’s rope) and the rigging count as part of the load.
If you have steel to put up or take down, see our steel erection and dismantling service. On a contract lift, our own appointed person plans the lift and writes the lift plan.
Section sizes
Reading the weight from the section size
A UB is the common I-shaped beam, deeper than it is wide. Its flanges are the top and bottom plates, and the web is the upright plate joining them. The size is written as three numbers, for example 305 x 165 x 40. The first two are the nominal depth and flange width in millimetres. The last is the mass per metre in kilograms.
The same depth and width come in several weights, made by rolling the web and flanges thicker or thinner, as SteelConstruction.info explains. British Steel rolls the 305 x 165 UB in weights from 40 to 54 kg/m.
All three numbers are rounded. British Steel’s universal beam datasheet gives the 305 x 165 x 40 UB a mass of 40.3 kg/m and an actual depth of 303.4 mm. Use the maker’s figure where you can find it.
Universal columns (UC), which are closer to square, and parallel flange channels (PFC), which are C-shaped, are named the same way. Their nominal dimensions and masses are set by BS EN 10365, and British Steel publishes datasheets for each range.
The table gives a few examples from British Steel’s datasheets for universal beams and for other sections, with the mass per metre as published and the weight of a 6 m length worked out from it. For any other size, use the maker’s table for that section.
| Section size | Type | Mass per metre (kg/m) | 6 m length (kg) |
|---|---|---|---|
| 152 x 89 x 16 | UB | 16.0 | 96 |
| 203 x 133 x 30 | UB | 30.0 | 180 |
| 305 x 165 x 40 | UB | 40.3 | 242 |
| 406 x 178 x 60 | UB | 60.1 | 361 |
| 533 x 210 x 92 | UB | 92.1 | 553 |
| 203 x 203 x 46 | UC | 46.1 | 277 |
| 200 x 90 x 30 | PFC | 29.7 | 178 |
RSJs and older beams
Many people call any steel beam an RSJ, short for rolled steel joist. Strictly, a joist is a separate section with tapered flanges, covered by BS 4-1 alongside UBs. A beam taken out of an older building may be a size no longer made and missing from current tables, so measure it and work from the cross-section, as shown below.
Worked examples
Steel beam weight in tonnes: worked examples
Divide kilograms by 1,000 for tonnes.
A 7.5 m universal beam
A 305 x 165 x 40 UB at 40.3 kg/m and 7.5 m long weighs 40.3 x 7.5 = 302 kg, or 0.30 t.
A 12 m universal beam
A 533 x 210 x 92 UB, 12 m long, weighs 92 x 12 = 1,104 kg. The 92 in the name is rounded and the table figure can be a little higher, so call it just over 1.1 t.
Rolling tolerances
A rolled beam can weigh slightly more or less than its table figure, because the rolling tolerances in BS EN 10034 allow a small difference in mass. Where the weight is close to what the crane or a sling can take, add a margin for this or have the piece weighed.
Work from the steel maker’s figures and the rigging maker’s instructions. In Great Britain, LOLER puts the planning of every lifting operation on a competent person, and Northern Ireland’s regulations say the same. On crane lifts, BS 7121-1 makes this the appointed person’s job.
Unknown size
Weight from measurements when there is no size
Where there is no size to go on, measure the beam. Take the overall depth and the flange width, then the thickness of a flange and of the web. Work out the area of steel in the cross-section and multiply it by the density of steel to get the mass per metre.
The Blue Book, the section tables produced by the Steel Construction Institute (SCI) for Steel for Life, calculates its masses per metre from a density of 7,850 kg per cubic metre. That works out at 0.785 kg/m for every cm² of cross-section.
An example
Say a beam measures 303 mm deep, with flanges 165 mm wide and 10 mm thick and a 6 mm web.
- Both flanges: 2 x 165 x 10 = 3,300 mm².
- Web, between the flanges: (303 – 20) x 6 = 1,698 mm².
- Total: 4,998 mm², or 49.98 cm².
- Mass per metre: 49.98 x 0.785 = 39.2 kg/m.
That is close to the 40.3 kg/m of a 305 x 165 x 40 UB. The sum comes out a little low because it leaves out the curved fillets where the web meets the flanges, so compare your answer with the tables and take the next heavier section.
What to add
Plates and fittings on the beam
A fabricated beam carries end plates, stiffeners, cleats and bolts, and the Blue Book’s masses leave them out: they are for the steel section alone, with no allowance for connecting material or fittings. If the beam came from a fabricator, ask for the piece weights from their drawings.
For flat plate, the same density gives 7.85 kg per square metre for each millimetre of thickness. A 20 mm end plate 500 mm by 250 mm is 0.125 m², so it weighs 0.125 x 20 x 7.85 = 19.6 kg. Two of them add 39 kg, taking the 7.5 m beam above from 0.30 t to 0.34 t.
Beams coming out of a building
A beam being taken out can carry much more than its own steel. Check what is still fixed to it: concrete casing, fire protection, brackets, pipework or cable tray. No table covers these, so estimate each one. Paint or galvanising adds a little more. Fittings at one end also move the centre of gravity away from the middle of the beam, which changes where the slings go. Our guide to the centre of gravity when lifting a load explains how to find it.
The lift
Adding the rigging to get the lift weight
HSE’s L113, its guidance on LOLER, lists the weight of the load among the things to consider when assessing the risks of a lift. It also says the lifting accessories and the hook block should sometimes be counted in the load, giving lifts by mobile crane as an example.
Add the hook block and all the rigging between it and the beam, such as the slings and shackles, to the total from the sections above. Each sling and shackle must be rated for its share. For the figures marked on them, see The Difference Between SWL and WLL.
The appointed person then checks the total against what the crane can lift at the radius where it picks up the beam and where it sets it down. Our guide What size crane do I need? explains how that works. Our LOLER guide covers the regulations in Great Britain.
From our lifts
Given a beam size and length, we also ask whether it has end plates, cleats or stiffeners welded on, whether it’s one piece or bolted sections, and whether anything is still attached. The weight per metre is only the start.
On steel coming out of an old building, we look at the steel itself before it’s lifted, not just the drawings, and allow for anything still attached to it.
Questions
Common questions
How heavy is a steel beam in kg?
A UK universal beam weighs from about 13 kg to 584 kg a metre, depending on its size: British Steel’s range runs from the 127 x 76 x 13 to the 1016 x 305 x 584. The last number of the size is the mass in kg per metre, so multiply it by the length for the whole beam.
What is the weight of a 250 mm beam per metre?
A 254 mm deep universal beam weighs 22 to 43 kg per metre in British Steel’s range, from the 254 x 102 x 22 to the 254 x 146 x 43. A 254 x 254 universal column, about as wide as it is deep, is much heavier at 73 to 167 kg/m.
What does RSJ stand for?
RSJ stands for rolled steel joist. People use it for almost any steel beam, though a true joist has tapered flanges and is a different section from a universal beam; both are covered by BS 4-1. Whatever it is called, find its full size on the drawing or delivery paperwork to read off its weight.
How much does an RSJ weigh?
An RSJ weighs its mass per metre multiplied by its length. For a universal beam the mass per metre is the last number of its size, so a 203 x 133 x 30 UB weighs 30 kg/m and a 3 m length weighs 90 kg. An older beam with no size can be measured instead.
How heavy is a 4 m RSJ?
A 4 m RSJ weighs about 101 kg if it is a 254 x 102 x 25 UB, which British Steel lists at 25.2 kg/m. A 305 x 165 x 40 UB of the same length comes to about 161 kg. For your own beam, multiply the mass per metre in its size by 4.
How heavy is a 20 ft steel beam?
A 20 ft steel beam is 6.1 m long, so multiply its mass per metre by 6.1. A 203 x 133 x 30 UB that long weighs about 183 kg, and a 305 x 165 x 40 UB about 246 kg. Add any end plates and fittings on top, as shown above.
How much does a 12 ft steel I-beam weigh?
A 12 ft steel I-beam weighs its mass per metre multiplied by 3.66, since 12 ft is 3.66 m. A 203 x 133 x 30 UB that long weighs about 110 kg, and a 254 x 146 x 37 UB about 135 kg. The table above gives the mass per metre for a few other sizes.
How do you calculate the weight of a steel beam?
Multiply the mass per metre by the length in metres. Where the size is known, the mass per metre is in its name and in the steel maker’s tables. Where it is not, measure the cross-section, work out its area in cm² and multiply by 0.785, from the 7,850 kg per cubic metre density the Blue Book uses.
How much does a steel beam weigh in pounds?
Multiply the weight in kilograms by 2.205 to get pounds, as 1 kg is about 2.205 lb. A 305 x 165 x 40 UB at 40.3 kg/m weighs about 89 lb per metre, or 27 lb per foot. For a whole beam, convert at the end: a 6 m length at 242 kg is about 534 lb.
Get help
Having your steel beams lifted
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