Rebar weight chart

The four tables an engineer reaches for most often, in one place: what a bar weighs, what area it gives you, what a spacing gives you per metre width, and how many 12 m lengths make a tonne.

Every number here comes from two constants — steel weighs 7850 kg/m³, and a bar is a circle — so none of it has to be memorised, only re-derived when you doubt it.

Mass and area, by bar size

T (written Y on older drawings — the same bar) is high-yield deformed bar, f_y 460 N/mm² in BS 8110 — 410 on some Nigerian mill certificates, which is a different design strength, so read the certificate rather than assuming. R is plain mild steel, f_y 250, still common for links. The mass per metre is the same either way: it depends on the geometry, not the grade.

Where d²/162 comes from

The rule everyone uses is not an approximation of a table — it is the table, with the constants folded together:

So a T16 is 256/162 = 1.58 kg/m, and you never need the chart again. The 162 is worth memorising; the nine rows above are not.

Steel area per metre width, by spacing

For slabs, walls, stairs and footings, where steel is specified as a size at a spacing rather than as a number of bars. Values are mm² per metre width.

Spacing in mm, centre to centre. The arithmetic is A_s = 1000 × (bar area) / spacing — one bar per spacing, across a metre.

Two limits worth remembering before picking a row: BS 8110 wants bars no further apart than 3d or 750 mm in a slab, and close enough for crack control where the slab is exposed. And the clear gap between bars must beat the aggregate size plus 5 mm — steel a concrete pour cannot get through is steel that is not there.

How much to order is not total length ÷ 12

Steel arrives in 12 m lengths and is sold by the tonne. The quantity you need is the sum of the cut lengths; the quantity you buy is however many 12 m bars those cuts can be got out of — and an off-cut is only useful if another bar fits inside it.

This is why a bar schedule's total mass and a merchant's invoice never agree, and why the gap is bigger the closer the cut length is to half a bar. Where cuts are long, order by the length. Where they are short and varied, the off-cuts nest and the two figures converge.

Structura does this packing for you — it lays the schedule out into 12 m lengths (or whatever stock length you set) and tells you how many to buy, erring towards one length too many rather than one too few. Bars longer than the stock length are flagged for lapping rather than quietly lapped: laps are a detailing decision.

Sense checks worth doing on any schedule

Reinforcement per cubic metre of concrete is the fastest way to catch a schedule that has gone wrong, because the ranges are narrow and well known:

These are ranges seen in ordinary Nigerian residential frames, not code values. Use them to catch a factor-of-ten error, not to justify a design.

Next

• Lap and anchorage lengths
• Concrete and block quantities
• Bar bending schedules
• Cover, grades and mixes
• Beam design
• Slab design
• Pad footing design
• All worked examples