Complete Engineering Guide to Bar Bending Schedules (IS 2502 & IS 456)
1. Cutting Length & Bend Deductions (IS 2502 Table V)
A bar bent round a mandrel follows the arc rather than the two straight legs, so the cut length is shorter than the sum of the dimensions taken to the outside of the bend. IS 2502 Table V states it directly: L = A + E − ½R − d, so a right-angle bend deducts ½R + d. Because the internal radius is R = kd, the deduction depends on the steel and the bar size — it is not a single number:
- Mild steel (k = 2): deduct 2d at 90°
- Medium tensile (k = 3): deduct 2.5d at 90°
- IS 1786 deformed (k = 4): deduct 3d at 90°
- IS 1786 above 25 mm (k = 6): deduct 4d at 90°
2. Hook and Bend Allowances (IS 2502 Table II)
IS 2502 Table II gives the hook allowance H and bend allowance B as functions of k, the internal bend radius in bar diameters (R = kd, Fig. 1 Note 1):k = 2 for mild steel, 3 for medium tensile and 4 for high strength deformed bars to IS 1786 — rising to 3, 4 and 6 respectively above 25 mm. H is then 9d, 11d, 13d or 17d, rounded to the nearest 5 mm and never less than 75 mm. A binder's straight portion beyond the end of the curve is never less than 8d (Cl 3.3), and cutting lengths are given to the next greater whole 25 mm (Cl 5.1.1).
3. Unit Weight Formula (D²/162)
Unit Weight (kg/m) = D² / 162
Where D is the nominal diameter in millimetres. The exact derivation from a steel density of 7,850 kg/m³ gives 162.19, but every printed Indian schedule writes 162 — a difference of 0.12%, and this calculator uses 162 so that its totals reproduce exactly when a checking officer recomputes them by hand. In CPWD DSR (Item 5.22), rebar is billed per quintal (100 kg) or metric tonne (1,000 kg).
4. 1D Stock Cut Optimization (12m Rods)
Steel reinforcement in India is delivered in standard 12-meter commercial stock lengths. QuickBOQ solves the 1D Bin Packing Cutting Stock problem to determine optimal nesting combinations, preventing off-cut scrap from exceeding standard 3% to 5% tender margins.