Metal Weight Calculator
Weight of bar, tube, plate and standard sections in 23 alloys — using published section masses, because the rectangle method loses the root fillets.
What the rectangle method loses, by family
Measured against the published tables. This is why there is no single "add a few per cent for fillets" factor — the error runs from five per cent light to marginally heavy depending on what you are weighing.
Why this disagrees with other calculators
A rolled I-section weighs more than its outline. Almost every metal weight calculator asks for depth, width and thicknesses and adds up rectangles. Real sections have generous root fillets where the web meets the flanges, and that material is in no outline. An IPE 200 comes out at 21.4 kg/m by rectangles and is published at 22.4 — nearly 5% adrift on dimensions you entered perfectly correctly. Over a few tonnes of steelwork that is real missing weight, in the direction that matters: the lift, the delivery and the invoice all come in heavier.
But it is not one correction factor. Measured against the tables here, the rectangle method runs 2.7–5.2% light on I-sections, about 1% light on angles and wide-flange shapes, and essentially nothing on channels — where it can even tip heavy, because tapered flanges give back roughly what the fillet took. Anyone applying a blanket "add 4%" is wrong on three families out of four. So standard sections here use published masses, and the tool shows what the rectangle method would have said next to it.
- Hollow sections run the other way. Square and rectangular tube has rounded outer corners, which take material away — about 4% on a 50×50×3. Those radii are modelled here at twice the wall thickness, which is what puts a 50×50×3 on its published 4.25 kg/m instead of a sharp-cornered 4.43.
- Hex bar is sized across the flats. Across corners is 2/√3 larger — about 15% — which is the number that catches people ordering stock to fit a socket.
- Density does more work than people expect. Swapping 304 stainless for mild steel adds about 2% on identical geometry; swapping aluminium for steel takes about two thirds off. If a substitution is being weighed up on mass grounds, the density ratio is the entire answer.
- The American designation states its own weight. A W12×26 is 26 lb/ft by definition. An IPE 300 gives you no such hint — you have to look up that it is 42.2 kg/m.
- These are nominal figures. Rolling tolerance on hot-rolled plate is not symmetrical — mills are paid by weight, and under-thickness is capped far more tightly than over-thickness — so real stock tends to sit at or above nominal rather than either side of it. For a crane lift or a shipping weight, round up.
How to use
- Choose a bar, tube or plate shape, or switch to a standard rolled section.
- Pick the alloy — density does more of the work here than people expect.
- Enter the length and how many pieces.
- Add a price per kilogram if you want the cost as well.
Frequently asked questions
Why does this disagree with other metal weight calculators?
Because most of them ask you for the depth, width and thicknesses of a beam and add up rectangles. A real rolled section has generous root fillets where the web meets the flanges, and that material is in no outline. An IPE 200 comes out at 21.4 kg per metre by rectangles and is published at 22.4, so a perfectly correct set of dimensions still lands nearly five per cent light. Standard sections here use published masses instead, and the tool shows what the rectangle method would have said next to it.
How much does the rectangle method actually lose?
It depends entirely on what you are weighing, which is the real lesson. Measured against the tables in this tool it runs 2.7 to 5.2 per cent light on I-sections, about one per cent light on angles and wide-flange shapes, and essentially nothing on channels — where it can even come out marginally heavy, because tapered flanges give back roughly what the fillet took. Anyone applying a blanket four per cent correction is wrong on three families out of four.
Why is a square tube lighter than my calculation?
Because it has rounded outer corners, and a sharp-cornered calculation counts material that is not there. On a 50 by 50 by 3 the difference is about four per cent: the sharp figure is 4.43 kilograms per metre and the published mass is 4.25. This tool models the corner radius at roughly twice the wall thickness, which is the figure the hollow section standards use and what puts the calculation back on the published mass. Note it runs the opposite way from beams, which is another reason not to trust one correction factor.
Is hex bar measured across the flats or the corners?
Across the flats, always, and the difference matters. Across corners is two over the square root of three larger, which is about fifteen per cent, so ordering by the wrong dimension gets you stock that will not fit the socket or will not go in the hole. The weight calculation follows the flats measurement too, since the area of a hexagon is the square root of three over two times the across-flats dimension squared.
How much weight does changing alloy save?
The density ratio is the entire answer, and it is worth knowing before redesigning anything. Aluminium is about a third the weight of steel for identical geometry, titanium a little under sixty per cent, and magnesium under a quarter. Going the other way, 304 stainless is about two per cent heavier than mild steel — a small figure that still matters on a big fabrication, and one people miss entirely when substituting stainless for a corrosion problem.
Can I use a published section in a different metal?
The tool will scale it for you, and the scaling is exact because the geometry does not change — it is just density ratio. What you should check is whether the section is actually rolled in that alloy, because most of the standard steel sections listed here are not made in aluminium or stainless. Aluminium extruded sections exist in their own range of profiles with their own tables, and substituting a steel designation into an aluminium order will not get you what you expect.
Will the real material weigh what this says?
Slightly more, usually. Rolling tolerance on hot-rolled plate is not symmetrical: mills are paid by weight, and under-thickness is capped far more tightly than over-thickness, so stock tends to sit at or above nominal rather than scattering either side of it. For anything where the number matters — a crane lift, a shipping weight, a trailer load — round up rather than treating the calculation as the final figure.
Why does the American beam designation include a number of pounds?
Because it literally states the weight. A W12 by 26 is 26 pounds per foot by definition, which works out at 38.7 kilograms per metre, and the 12 is the nominal depth in inches. It is a genuinely useful naming convention: you can read the mass straight off the designation without a table. European designations give you no such hint, which is why you have to look up that an IPE 300 is 42.2 kilograms per metre.
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