Rebar Quantity Takeoff and the Bar Bending Schedule
Rebar is bought by weight but detailed by length and shape. The bar bending schedule bridges the two — and it is where most steel is over- or under-ordered.
Unit weight by diameter
| Bar (mm) | kg/m |
|---|---|
| 10 | 0.617 |
| 12 | 0.888 |
| 16 | 1.578 |
| 20 | 2.466 |
| 25 | 3.854 |
Cutting length
- Standard hook (90° or 135°): add 9d–12d per hook.
- Lap splice: add 40d (tension) or 50d in critical zones; count one lap per 12 m bar length for long runs.
- Bend deduction: subtract ~2d per 90° bend, ~3d per 135°, ~0.5d per 45° (the neutral axis shortens on a bend).
Stirrups and ties
One stirrup length = 2(a + b) − bend deductions + 2 hooks (10d each)
where a and b are the tie dimensions to the centre of the outer bars.
Worked slab strip
4.0 m clear span slab, 12 mm main bars at 150 mm c/c, 20 mm cover, standard hooks both ends:
Cutting length = 4000 − 40 + 2(9 × 12) = 4176 mm
Weight = 21 × 4.176 × 0.888 = 77.9 kg (one direction)
Add distribution steel the other way, then 3–5% wastage and offcuts, and convert to commercial 12 m lengths for ordering.
EngEst Pro’s Structural Calculator builds the bar schedule from element dimensions — it computes cutting lengths with hooks and laps, stirrup counts, converts to weight by diameter, and outputs RSB quantities per bar size in the BOM.
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