LEINSTER STEELBar is sold by weight, so the size on your cut list and the price on your invoice are connected by one number: kilograms per metre. Knowing it saves you two arguments — one with the man loading the van about whether it'll fit, and one with yourself about whether the quote looks right. Here are the figures for the sizes that actually move through a yard, along with the formulas so you can do the ones that don't.
Flat bar sizes and weights
Flat bar is described width × thickness in millimetres — a 50x10 is 50mm across the face and 10mm thick. Standard mill lengths are 6m.
| Size (W × T, mm) | Weight (kg/m) | 6m length (kg) |
|---|---|---|
| 20 × 5 | 0.79 | 4.7 |
| 25 × 5 | 0.98 | 5.9 |
| 25 × 6 | 1.18 | 7.1 |
| 30 × 5 | 1.18 | 7.1 |
| 30 × 6 | 1.41 | 8.5 |
| 40 × 5 | 1.57 | 9.4 |
| 40 × 6 | 1.88 | 11.3 |
| 40 × 10 | 3.14 | 18.8 |
| 50 × 6 | 2.35 | 14.1 |
| 50 × 8 | 3.14 | 18.8 |
| 50 × 10 | 3.92 | 23.5 |
| 60 × 10 | 4.71 | 28.3 |
| 65 × 8 | 4.08 | 24.5 |
| 75 × 6 | 3.53 | 21.2 |
| 75 × 10 | 5.89 | 35.3 |
| 75 × 12 | 7.07 | 42.4 |
| 100 × 10 | 7.85 | 47.1 |
| 100 × 12 | 9.42 | 56.5 |
| 150 × 10 | 11.78 | 70.7 |
| 150 × 12 | 14.13 | 84.8 |
For a size not listed: width × thickness ÷ 127.4 = kg per metre. It works because mild steel weighs 7,850kg per cubic metre, and that constant folds the unit conversion in for you. A 90x8 flat is 720 ÷ 127.4, near enough 5.65kg/m.
Round bar sizes and weights
Round bar is given by diameter alone. The weight climbs with the square of the diameter, which is why a 40mm round is four times the weight of a 20mm rather than twice — worth remembering before you send one man out to collect it.
| Diameter | Weight (kg/m) | 6m length (kg) |
|---|---|---|
| 8 mm | 0.39 | 2.4 |
| 10 mm | 0.62 | 3.7 |
| 12 mm | 0.89 | 5.3 |
| 16 mm | 1.58 | 9.5 |
| 20 mm | 2.47 | 14.8 |
| 25 mm | 3.85 | 23.1 |
| 30 mm | 5.55 | 33.3 |
| 32 mm | 6.31 | 37.9 |
| 40 mm | 9.86 | 59.2 |
| 50 mm | 15.41 | 92.5 |
The formula here is diameter² ÷ 162.2 = kg per metre. A 45mm round: 2,025 ÷ 162.2 = 12.5kg/m.
Figures are calculated at a density of 7,850 kg/m³ and rounded to two decimals. Hot rolled bar carries a rolling tolerance, so an actual length may weigh a fraction either side. Bar is priced on these nominal weights.
Picking a size for the job
Most bar work is judgement rather than calculation, and the sizes settle into habits. 25x5 and 30x5 flat is strapping, hinge plates and light brackets. 50x10 is the workhorse for gate frames, drag bars and anything that takes a knock. 75x10 and 100x10 turn up as base plates, packers and fixing plates under posts. On the rounds, 10mm and 12mm are pins, stays and infill on railings; 25mm to 40mm is shafts, axles and repairs where something has to turn or take a shear load.
Two things to watch. Bar bought for a structural connection — a base plate or a splice — should come off a drawing, not off a chart, and it needs the right grade: our S275 vs S355 guide covers when that matters. And if you're spanning anything, bar is the wrong product; that's a job for universal beam or PFC channel. For what's in stock and the finishes available, see the main flat and round bar page.
Common questions
How do you work out the weight of steel flat bar?
Width in mm × thickness in mm ÷ 127.4 = kg per metre. A 50x10 is 500 ÷ 127.4 = 3.92kg/m, so a 6m length is about 23.5kg.
How much does a 6m length of 20mm round bar weigh?
About 14.8kg — one man's lift. A 50mm round over the same length is 92.5kg, which is not.
What's the difference between flat bar and strip?
In practice, nothing. Hot rolled flat bar has slightly rounded edges and mill scale; bright or cold rolled strip has square edges and a cleaner face. Gates, brackets and general fabrication get hot rolled.
Do you cut bar to length?
Yes, free of charge, same day on stock sizes, black or sandblasted and primed. Send a cut list on the enquiry form and we'll cut to it.
Is there a minimum order?
€100 ex VAT, made up from any mix of sizes. Single cut lengths are fine — you don't have to take a bundle.
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