Rebar Weight Chart and Bar Bending Schedule Basics
The d²/162 rule turns rebar drawings into kilograms in seconds. Here is how it works, plus how stirrups and bend deductions affect the tonnage.
What a bar bending schedule is
A BBS (bar bending schedule) lists every rebar shape on the job: diameter, shape code, cutting length, number of pieces and weight. It is the bridge between the drawing and the steel supplier: the yard cuts and bends exactly to this list, and you buy steel by the total weight it produces.
The d²/162 rule
Weight in kg per metre = d² ÷ 162, with d the bar diameter in millimetres. It is nothing mysterious: it is the round-bar volume (π/4 × d²) multiplied by the density of steel, 7,850 kg/m³, simplified into one constant. So a 16 mm bar is 16² ÷ 162 ≈ 1.58 kg/m.
Standard sizes at a glance
US customary sizes with metric equivalents: #3 (9.5 mm) ≈ 0.56 kg/m, #4 (12.7 mm) ≈ 0.99, #5 (15.9 mm) ≈ 1.55, #6 (19 mm) ≈ 2.24, #8 (25.4 mm) ≈ 3.97. European sites use the millimetre names directly — 8, 10, 12, 16, 20, 25 mm — with the same formula.
Stirrups and bend deductions
A stirrup's cutting length is its perimeter plus hook lengths minus a small deduction at every bend, because the outer corner stretches while the inner corner compresses. A common allowance is 0.5 × diameter per 45° bend and 1 × diameter per 90° bend — codes vary, so follow your project spec. Small per-bar errors multiply by the hundreds of stirrups on a real pour.
Calculate the takeoff in one pass
The Rebar calculator turns a bar list into total length and weight (with a CSV export for the schedule) and sizes stirrup packages, hooks and bend deductions included.
Rebar bending: spacing, hooks and the bend test
Bending rebar does not change its weight, but it changes how much you need. Standard hooks (90-degree and 180-degree seismically bent ends) add 10-15 bar diameters of extra length per bend, so a 12 mm bar with two 180-degree hooks needs about 36 cm more raw bar than the straight span. Minimum bend diameter is 4d for bars up to 16 mm and 7d above that - a 20 mm bar needs a 140 mm mandrel. Because bending dimensions come from the structural drawing, weight stays a pure length calculation: use the table above and add the hook allowances.
Weight per bar and per tonne: quick answers
The two most common shopping questions have simple answers. Per bar: a standard 12 m bar of 12 mm rebar weighs 12 x 0.888 = 10.7 kg, an 8 mm bar 4.7 kg, a 16 mm bar 19.0 kg. Per tonne: one tonne of 12 mm rebar is about 94 bars, of 8 mm rebar about 253 bars, of 16 mm about 53 bars. Our Rebar calculator converts any diameter, length and quantity into total weight instantly, in kg or tonnes.