Bar Bending Shape Generator

About Bar Bending Schedule (BBS) and IS 2502

Bar Bending Schedule (BBS) is the master list of all reinforcement bars on a project — each row specifies: bar mark, shape code, bar diameter, leg dimensions, cut length, number of bars, and total weight. The BBS is what the rebar yard reads to cut + bend + deliver pre-fabricated steel to site. Without an accurate BBS, the contractor either over-orders (wasting 15-25% steel) or under-orders (causing site stoppage waiting for re-bending).

IS 2502:1963 (Reaffirmed 2014) codifies the 9 standard reinforcement bar shapes used in Indian RCC construction. Each shape has a 2-digit code (00, 13, 14, 20, 21, 33, 35, 41, 51) — the same codes appear on every Indian site drawing, every BBS spreadsheet, every rebar yard's job ticket. Standardizing these shapes means designers, detailers, and benders speak the same language.

The 9 standard shape codes

• Code 00 — Straight bar: main bars in beams, columns. Cut length = total length.
• Code 13 — L-bend (90°): main bars at column-beam junctions, slab edge.
• Code 14 — U-bend: open stirrup ties, anchorage bars, beam end-hooks.
• Code 20 — Z-bend: chair bars, top-reinforcement at supports.
• Code 21 — Closed stirrup: column lateral ties + beam stirrups. The workhorse shape for shear reinforcement.
• Code 33 — Right-angle crank: bent-up bars for beam top reinforcement at supports.
• Code 35 — Helical: spiral reinforcement for circular columns (per IS 13920 ductile detailing).
• Code 41 — Crank with hook: diagonal anchorage at beam-column joints (seismic detailing).
• Code 51 — Closed hoop / diamond: confined-concrete stirrup pattern for seismic Zone IV/V columns.

How BBS calculations work

The cut length for each shape uses the straight-line dimension PLUS / MINUS adjustments for bends. Each bend reduces the cut length (the bar travels along the inside of the curve, shorter than the outside). IS 2502 Table 1 specifies the bend deduction:

• 90° bend: deduct 2 × bar diameter
• 135° bend (hook): deduct 3 × bar diameter
• 180° hook: deduct 4 × bar diameter
• 45° crank: deduct 1 × bar diameter

Example: a 16 mm diameter Code 21 stirrup with 200 × 300 mm outer dimensions has perimeter 1000 mm; with 4 × 90° bends → 128 mm deduction; plus 2 × 135° hooks (10 × dia each) → 320 mm added. Final cut length = 1192 mm. The generator does all this automatically per IS 2502.

Common BBS mistakes

1. Wrong shape code — using Code 14 (U-bend) instead of Code 21 (closed stirrup) means open-bottom stirrups; shear capacity 30% lower than design. The bend yard cuts as specified — get the code right.
2. Forgetting hook length — IS 2502 hook = 10 × bar diameter for 90° (round) hooks; some sites use only 5 × dia, weakening anchorage.
3. Hand-calculated cut length errors — manual BBS often has 2-5% cumulative error; over a 100-tonne steel job, that's 2-5 tonnes of over- or under-ordered steel. Use generator output as the master.
4. No 135° hook on stirrups in seismic zones — IS 13920 Cl. 7.3.2 requires 135° hooks for ductile detailing. Many sites use 90° hooks; non-compliant.

Related references

• IS 2502:1963 — Bar bending schedule (the primary code)
• IS 456:2000 — RCC code (defines anchorage + lap length)
• IS 1786:2008 — TMT rebar specification (the steel)
• IS 13920:2016 — Ductile detailing (specifies 135° hooks for seismic)
• InfraLens BBS Calculator — quantity + weight calculator for full reinforcement
• InfraLens CAD Library — more parametric DXF generators
• Standard hook lengths (Handbook) — quick reference for hook + lap lengths