Bend Deduction Calculator

Why Contractors Lose Money Here

Bar dimensions on drawings are measured to the outside of the bar, but a bent bar is longer on the outside of each bend than the steel actually used. Cutting to the plain sum of dimensions wastes steel on every bend; across a building's BBS that adds up to tonnes.

Real Site Example

A 12 mm L-bar with legs of 1,500 mm and 500 mm (one 90° bend): sum = 2,000 mm; deduction = 2 × 12 = 24 mm; cutting length = 1,976 mm. A U-bar with two 90° bends in 16 mm bar deducts 2 × 32 = 64 mm.

Professional Best Practices

Write the bend count and the deduction into each BBS line, so the checker can see how the cutting length was reached, and test one bent bar against the drawing before cutting the batch.

Engineering Checklist

• Measure dimensions out to out, as drawings show them
• Count every bend and its angle, including the bends that form hooks
• 45° = 1d, 90° = 2d, 135° = 3d, 180° = 4d
• Add hook lengths separately where the shape has hooks
• Bend a trial bar before cutting the batch

Government & Standards References

• IS 2502 — Code of practice for bending and fixing of bars for concrete reinforcement
• SP 34 — Handbook on Concrete Reinforcement and Detailing
• IS 456:2000 — Clause 26.2.2 (anchorage, hooks and bends)

How Experienced Contractors Handle This

BBS checkers recompute a sample of lines by hand — sum of dimensions less bend deductions plus hooks — before the schedule goes to the bar bender.