The Bar Bending Schedule Calculator generates IS 2502:1963-style BBS tables from member dimensions — total length, cutting length, weight per bar, and total weight per bar diameter — for slabs, beams, columns, footings, and staircases. Output is downloadable as Excel (with formulas), CSV, or PDF.
Use it during structural drawing review to verify the contractor's BBS, during execution as a cutting-list reference, and during billing for measurement against IS 1200 Part-8 conventions.
Per IS 2502:1963 Table 1 — bend deductions: 90° bend = 2d (where d is bar diameter), 135° bend = 3d, 180° hook = 8d (for full hook) or 6d (semi-circular). Cranks at supports: cranked length = (D − 2 × cover) × √2 + horizontal projection. Lap length: 50d for tension (Fe415), 60d for tension (Fe500), 40d for compression. The calculator subtracts bend deductions from straight-bar geometric length to derive cutting length.
W = d² / 162 (kg/m) where d is in mm. Standard values: 8mm = 0.395 kg/m, 10mm = 0.617, 12mm = 0.888, 16mm = 1.578, 20mm = 2.466, 25mm = 3.852, 32mm = 6.313. These are the IS 1786:2008 nominal weights — actual weights for Fe500D HYSD bars are within ±3.5% of nominal per the standard's tolerance band.
Inputs: short span Lx, long span Ly, slab thickness, cover, main bar diameter and spacing, distribution bar diameter and spacing. The calculator computes: number of main bars = (Ly − 2cover) / spacing + 1; main bar cutting length = Lx − 2cover + 2 × bend deduction (cranks); total weight = N × cutting length × W/m. For two-way slabs, it generates a separate row for each direction.
Slab 4m × 5m × 150mm thick, M25, Fe500. Cover 25mm. Main bars 10mm @ 150mm c/c (short direction); distribution 8mm @ 200mm c/c (long direction). Number of 10mm bars: (5,000 − 50) / 150 + 1 = 34 bars. Cutting length per 10mm bar: 4,000 − 50 + 2 × (45° crank: 0.42 × (150−50)) = 3,994mm = 3.994m. Total 10mm steel: 34 × 3.994 × 0.617 = 83.8 kg. Distribution 8mm bars: (4,000 − 50) / 200 + 1 = 21 bars × (5,000 − 50 + 2 × 9d hooks) × 0.395 = 21 × 5,094 × 0.395 / 1000 = 42.3 kg. Total slab steel: 126 kg, or 6.3 kg/m² — within typical 5-7 kg/m² band for residential slabs.
Steel density is 7,850 kg/m³ ≈ 7.85 g/cm³. Cross-section area of a round bar = π × d² / 4 (mm²) = π × d² / 4 × 10⁻⁶ m². Weight per metre = area × 1m × density = π × d² / 4 × 10⁻⁶ × 7,850 = d² × 6.165 × 10⁻³ ≈ d² / 162.16. The 162 figure is the rounded simplification used in Indian practice. ACI 318 / BS 8110 use slightly different constants because of different density assumptions (~7.86 kg/m³).
IS 2502 Table 1: 90° bend = 2d, 135° = 3d, 180° hook = 8d (full) or 6d (half-hook). These are the lengths to subtract from the straight-bar geometric length to get the cutting (or actual) length, because bending changes the centerline path. For a 90° corner of a stirrup: deduct 4d for two corners (2 × 2d). For a 135° hooked stirrup tail: deduct 3d × 2 = 6d for both ends.
Cutting length is the actual physical length of the bar to be cut from stock — what the workman uses. Development length (Ld) is the length of bar embedded in concrete required to develop full design strength via bond — typically 47d for M20 / Fe415 or 47-58d depending on grade combination. They serve different purposes: cutting length is for material take-off, development length is for detailing the rebar layout (where laps go, where bars terminate).
Lap length is the overlap between two bar lengths spliced end-to-end, providing continuity of force transfer through bond with concrete. Per IS 456 Cl. 26.2.5.1: tension lap 50d (Fe415) or 60d (Fe500); compression lap 40d. In flexural members, laps should be staggered such that no more than 50% of bars are spliced at one section. The BBS lists laps as separate items so the contractor orders enough stock.
Use the structural drawing dimensions exactly — including cover, bar diameter, and bend allowances — and let the calculator compute to mm. Round only the final cutting-length column to the next 10mm (rebar is typically cut to 10mm precision at site). Round total weight to two decimal places (kg). Avoid pre-rounding inputs because errors compound across hundreds of bars.