Crank Bar Cutting Length Calculator

Why Contractors Lose Money Here

Crank bars are where slab steel estimates most often go wrong: the incline, the anchorage and the bend deductions are each small, but missing one makes every bar in the slab too short or too long.

Real Site Example

Slab with 3.0 m clear span, 150 mm thick, 20 mm top and bottom cover, 10 mm Fe500 bars in M20: Ld = 10 × 435 / (4 × 1.2 × 1.6) = 566 mm. D = 150 − 20 − 20 − 10 = 100 mm. Cutting length = 3,000 + 2 × 566 + 2 × 0.414 × 100 − 4 × 10 = 4,176 mm (cut 4,180 mm). At 300 mm spacing over a 4 m width: 14 bars, 58.5 m, 36.1 kg.

Professional Best Practices

Detail main bars and crank bars as separate BBS lines, and confirm crank positions (commonly L/4 from simply supported ends and L/7 near continuous supports, as the drawing shows) before bending.

Engineering Checklist

• Take D after deducting both covers and one bar diameter
• Use the anchorage on the drawing; otherwise Ld per IS 456
• Deduct 1d for each 45° bend (four per crank bar)
• Count only the cranked bars at their own spacing
• Cut and bend one trial bar before the batch

Government & Standards References

• IS 456:2000 — Clause 26.2.1 (development length), Clause 26.4 and Table 16 (cover)
• IS 2502 — bending and fixing of bars for concrete reinforcement
• SP 34 — Handbook on Concrete Reinforcement and Detailing

How Experienced Contractors Handle This

Estimators prepare the slab BBS bay by bay, separating main, crank, distribution and extra top bars, and total weight by diameter for the steel order.