How to use the Bar Bending Schedule (BBS) Calculator
- 1. List your barsOne line per bar mark: mark, shape letter, dia, number of bars and dimensions in mm.
- 2. Check the thumb rulesHook allowance, 45°/90°/135° bend deductions and the crank factor are all editable.
- 3. Get the scheduleCutting length, total length and weight for every mark, plus totals for each diameter.
How cutting length is worked out
A bar is drawn with out-to-out dimensions, but when it is bent it stretches at the bend, so the straight lengths add up to more than the bar you need. A bend deduction corrects this. Common site thumb rules are 1d for 45°, 2d for 90° and 3d for 135° (d = bar diameter). A 180° hook adds about 9d per hook (IS 2502 standard hook); many offices round it to 10d.
- Straight bar with two hooks: L + 2 × 9d
- L-bar: a + b − 2d
- U-bar: a + b + c − 2 × 2d
- Cranked bar: L + 0.42D per crank − 2 × 1d per crank (D = crank height)
- Rectangular stirrup: 2(a + b) + 2 × 10d − 3 × 2d − 2 × 3d
Weight per metre = D²/162 kg (D in mm), which comes from 7850 kg/m³ × πD²/4.
Worked example and site tips
A slab bent-up bar of 12 mm, clear length 3000 mm, crank height 150 mm, two cranks: 3000 + 2 × 0.42 × 150 − 4 × 1 × 12 = 3078 mm. Five such bars weigh 5 × 3.078 × 0.889 = 13.68 kg.
- Write one line per bar mark exactly as in the drawing, so the BBS can be checked mark by mark.
- Laps for bars longer than 12 m are not included. Add them to the length or use the allowance.
- In exams, state the deduction values you used. Different books use slightly different hook lengths.
- Always round cutting lengths to the nearest 5 or 10 mm on site.
Frequently asked questions
What is a bar bending schedule?
A BBS is a table listing every bar mark with its shape, diameter, number, cutting length and weight. Site teams use it to cut and bend steel and to order steel by weight.
Why do we deduct length at bends?
Bar dimensions are measured to the outer faces. At a bend the bar stretches, so the straight dimensions add up to more than the actual bar. The deduction (1d, 2d, 3d) corrects this.
Is the hook length 9d or 10d?
IS 2502 gives a standard hook that works out to about 9d for the extra length. Many offices use 10d for stirrup hooks. Both are editable here.
Is this calculator free?
Yes. You fill a short form once to see your result, and other Uncodemy tools then open without the form. Everything is calculated in your browser and nothing you type is uploaded.