BBS Calculator: Cutting Length and Steel kg
Calculate bar cutting length, count and steel kg by shape or by member, then download the BBS. An 8 mm stirrup for a 230 × 450 mm beam with 25 mm cover gives 1,224 mm using the default site shortcut.
For steel quantity, member mode gives a 4 × 3 m slab mesh of 12 mm bars at 150 mm and 8 mm bars at 200 mm as 98.09 kg. Every result shows its working; bend deductions, hook extensions, rounding and unit weight are editable.
All dimensions are in mm. Defaults are worked examples, not reinforcement design. Enter the dimensions, cover and reinforcement from your approved drawing.
A and B are concrete dimensions. Cover is measured to the outside of the stirrup. One closed two-legged stirrup has three 90° bends and two 135° hooks.
Conventions: edit bends, hooks, rounding and weight
Defaults: 1d / 2d / 3d site deductions; max(10d, 75 mm) stirrup extension (IS 13920:1993). IS 13920:2016 originally used 6d / 65 mm; Amendment 1 changes relevant link clauses to 8d / 75 mm. Edit both extension fields to match your specified edition. Table VIII mode uses its bundled allowance and ignores stirrup hook/deduction fields. These methods are not interchangeable fabrication details. Read sources and dimension conventions.
Steel weight
9.659 kg
Scheduled total length
24.48 m
Number of bars / pieces
20
Unit weight uses 7,850 kg/m³ density, matching the steel calculator. Stirrups use the editable site shortcut. Cuts and weights are unrounded internally.
| Mark / bar | Dia mm | Count | Cut mm | Total m | kg/m | kg |
|---|---|---|---|---|---|---|
| S1: stirrup | 8 | 20 | 1,224 | 24.48 | 0.395 | 9.659 |
| Total steel | 9.659 kg | |||||
Steel by diameter
- 8 mm: 24.48 m × 0.394584 kg/m = 9.659 kg
Step-by-step working
S1 · stirrup
- A after cover = 230 − 2 × 25 = 180 mm.
- B after cover = 450 − 2 × 25 = 400 mm. Outside stirrup dimensions; do not subtract diameter again.
- Each 135° hook extension = max(10 × 8, 75) = 80 mm.
- Site approximation: 2 × (180 + 400) + 2 × 80 − (3 × 2 + 2 × 3) × 8 = 1224 mm.
- Three 90° bends and two 135° hooks. This shortcut is not a bend-radius fabrication model or the IS 2502 Table VIII shape formula.
- Calculated length = 1224 mm; scheduled length = 1224 mm (unrounded).
- 20 × 1224 / 1000 = 24.48 m; × 0.395 kg/m = 9.659 kg (full precision used).
Opens in Excel. Includes input dimensions, conventions, working, diameter summary and totals.
How to use the bar bending schedule calculator
- Choose a shape for one bar mark, or member mode for a slab, beam, column or footing.
- Enter diameter and dimensions in mm. Check whether your drawing dimensions are concrete, outside bar, inside bar or centreline dimensions.
- Open Conventions and match the approved bending schedule. Use 25 mm rounding only when that scheduling convention applies.
- Review each cutting length and count before downloading the CSV. Use separate calculations for different spacing zones or reinforcement details.
For weights from an existing cutting list, use the steel calculator. For bar marks, schedule columns and checking workflow, read the bar bending schedule guide. Full schedules with drawings are in the member-wise BBS worked examples for slab, beam, column and footing.
BBS in under a minute
BBS before the steel order
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A BBS from your GFC drawings lists bar marks, cutting lengths and kg by diameter, so the steel order is not a guess. For one Delhi basement house it came to 17,470 kg from footings to plinth.
Offer in the video: First project 50% off (up to ₹5,000), minimum ₹2,500.
BBS full form: bar bending schedule and steel weight
BBS stands for bar bending schedule: a bar-by-bar list of shape, diameter, cutting length, count and weight. Steel weight is about D²/162 kg per metre (D in mm), so a 12 mm bar 6 m long weighs about 5.33 kg.
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Cutting length worked examples for every shape
Cutting length = bar dimensions after cover + hook allowances − bend deductions; rings and helices use the bar centreline. All dimensions are mm, with site deductions of 1d / 2d / 3d for 45° / 90° / 135° bends.
| Shape | Inputs | Working |
|---|---|---|
| Straight bar | 12 mm; overall 3,000; cover 25; no hooks | 3,000 − 2 × 25 = 2,950 mm. |
| Straight bar with two hooks | Same straight portion; complete allowance 110 mm per hook | 2,950 + 2 × 110 = 3,170 mm. The example allowance is 9 × 12 = 108 mm rounded to 110 for the Table II k = 2 hook; it is not a universal TMT hook. |
| L-bar | 12 mm; overall legs 3,000 and 600; cover 25 | Outside legs 2,950 and 550. Cut = 2,950 + 550 − 2 × 12 = 3,476 mm. |
| U-bar | 12 mm; overall legs 3,000, 600, 600; cover 25 | Outside legs 2,950, 550, 550. Cut = 4,050 − 2 × (2 × 12) = 4,002 mm. |
| 45° cranked bar | 12 mm; overall projection 3,000; cover 25; two rises of 150 | 2,950 + 2 × (√2 − 1) × 150 − 4 × 12 = 3,026.264 mm. Each crank replaces 150 mm horizontal projection and has two bends. |
| Rectangular stirrup | 8 mm; concrete 230 × 450; cover 25; two 135° hooks | 2 × (180 + 400) + 2 × max(10 × 8, 75) − 3 × (2 × 8) − 2 × (3 × 8) = 1,224 mm. |
| Circular tie / ring | 8 mm; concrete diameter 500; cover 25; explicit closure allowance 160 | Centreline diameter = 500 − 50 − 8 = 442. Cut = π × 442 + 160 = 1,548.584 mm. The 160 mm closure is an example input, not a design rule. |
| Helix | 8 mm; concrete diameter 500; cover 25; pitch 100; 10 turns; no end allowance | 10 × √[(π × 442)² + 100²] = 13,921.801 mm body length. Enter end turns or anchorage separately; number of identical helices multiplies this whole length. |
For 20 example stirrups: 20 × 1.224 = 24.48 m; 24.48 × 0.3945840373 = 9.659 kg. D²/162 gives 9.671 kg. Rounding each cut up to 1,225 mm first gives 24.50 m and 9.667 kg on the default weight basis.
Member steel quantity: a 4 m × 3 m slab mesh
One layer of this slab mesh weighs 98.09 kg before laps. Inputs: 25 mm cover, 12 mm main bars at 150 mm across the 3,000 mm width, 8 mm distribution bars at 200 mm along the 4,000 mm length, straight ends and no lap or anchorage length.
- Main count = ceil((3,000 − 50 − 12) / 150) + 1 = 21 bars. Each cut is 4,000 − 50 = 3,950 mm. Total = 82.95 m; weight = 73.644 kg.
- Distribution count = ceil((4,000 − 50 − 8) / 200) + 1 = 21 bars. Each cut is 3,000 − 50 = 2,950 mm. Total = 61.95 m; weight = 24.444 kg.
- Total = 98.089 kg, using full precision before display rounding. This is mesh quantity only.
Footing mode uses the same two-direction mesh calculation with your footing cover and layer count. Beam mode adds top bars, bottom bars and two-legged stirrups. Column mode adds vertical bars and rectangular ties. Specify the actual counts and spacing; the calculator does not check loads or detailing adequacy.
Conventions and sources: what the numbers mean
A hook tail, complete hook allowance and bend deduction are different quantities. Match both the shape and its dimension convention before comparing cutting lengths.
| Item | Default / editable alternative | Basis and source |
|---|---|---|
| Bend deductions | 45° = 1d; 90° = 2d; 135° = 3d. All editable. | Site approximations, not an IS 2502 universal table. IS 2502:1963, clauses 3.1–3.2 and shape tables use defined bending dimensions and allowances. |
| 135° stirrup extensions | max(10d, 75 mm). Change factor and minimum to the project detail. | IS 13920:1993, clause 6.3.1. The original 2016 edition used 6d / 65 mm; Amendment 1 (2017), clauses 6.3.1(a) and 7.4.1 changes relevant provisions to 8d / 75 mm. The default is explicitly the older convention. |
| Rectangular stirrup method | Site: 2(a+b) + 2t − 3(2d) − 2(3d), with outside dimensions a, b and extension t. Alternative: IS 2502 Table VIII shape A. | The alternative uses 2(A+E)+24d with inside dimensions shown in Table VIII. It includes its own allowance; do not add tails again. It does not establish an IS 13920 seismic detail. |
| Straight-bar end hooks | Zero hooks initially; complete allowance entered in mm. | IS 2502 Table II: H = 9d, 11d, 13d or 17d for k = 2, 3, 4 or 6; rounded to nearest 5 mm, minimum 75 mm. Choose the specified bar and bend detail. |
| Rounding | No rounding initially; optional round-up to 25 mm. Weight then uses scheduled length. | IS 2502 clause 5.1.1; also SP 34:1987 clause 13.3.3.1, printed p.197. |
| Schedule dimensions | Concrete dimensions minus cover, as labelled. Circular/helix diameter also subtracts one bar diameter for centreline length. | SP 34:1987, Appendix B, B-3 and B-6 distinguishes bending dimensions, bend corrections and schedule fields. Its reproduced ISO convention uses outside dimensions except radii; do not mix this with another shape table. |
| Unit weight | πd²/4 × 0.00785 kg/m by default; optional D²/162. | Reuses the existing steel calculator density calculation. D²/162 is an approximation, about 0.121% higher. |
| Cranks and helices | Crank addition uses √2 − 1, not rounded 0.42. Helix uses √[(πD)² + pitch²] per turn. | Geometric calculations. Enter actual centreline rise, pitch, turns and any end allowance. These are not code-selected dimensions. |
The example stirrup has outside dimensions 180 × 400 mm and inside dimensions 164 × 384 mm. Table VIII shape A gives 2(164 + 384) + 24 × 8 = 1,288 mm, or 1,300 mm rounded up. That differs from the 1,224 mm site shortcut because the shape allowance and dimension basis differ. Neither figure replaces the project’s approved bend radius and hook detail.
Common BBS mistakes to avoid
- Subtracting cover twice. If a schedule already gives outside bar legs, enter zero cover in shape mode.
- Counting across the wrong direction. Bars running along the length are counted across the width.
- Using floor instead of ceiling for intervals. This can leave spacing larger than the entered maximum when both edge bars are required.
- Adding hook allowances twice. A complete hook allowance already includes its curve; it is different from the straight tail beyond that curve.
- Using one spacing over a whole seismic member. End zones and midspan may differ. A uniform-spacing estimate does not check ductile detailing.
- Treating mesh weight as an order quantity. Add approved laps, chairs, starters and cutting waste separately. Rolling variation is not a reason to alter the cutting length.
SiteSetu prepares BBS with BOQ from your drawings. For measurements and running-account work, see the billing desk.
Frequently asked questions
What does this BBS calculator calculate?
Cutting length, bar count, total length and steel weight in kg, for seven bar shapes or four members (slab, beam, column, footing). Member mode gives a bar bending schedule with a diameter-wise steel summary. It measures the reinforcement you enter; it does not design it.
What is the cutting length of an 8 mm stirrup for a 230 × 450 mm beam?
1,224 mm by the common site shortcut, or 1,225 mm rounded up to 25 mm. With 25 mm cover, the stirrup’s outside size is 180 × 400 mm: 2(180 + 400) + 2(80) − [3(16) + 2(24)] = 1,224 mm. Use your approved bend and hook detail for fabrication.
Are 1d, 2d and 3d bend deductions prescribed by IS 2502?
No. They are common site approximations, editable here. IS 2502 gives shape-specific bending dimensions and allowances instead. Use the approved shape, radius and dimension convention for the final cutting list.
Should a 135° hook extension be 10d or 8d?
It depends on the code edition your drawings follow. The default max(10d, 75 mm) is from IS 13920:1993. IS 13920:2016 first used 6d with a 65 mm minimum; Amendment 1 (2017) changed this to 8d with a 75 mm minimum. Edit both fields to match your project.
Why does this calculator show two steel weight formulas?
The default matches our steel calculator: πd²/4 × 0.00785 kg/m. D²/162 is the site shortcut, about 0.12% higher, and you can switch to it under Conventions. A 12 mm bar is 0.887814 kg/m by the default and 0.888889 kg/m by D²/162. Don’t round kg/m before multiplying.
How are mesh bars and stirrups counted?
With a bar at each edge, count = ceil((distribution dimension − 2 × cover − bar diameter) / spacing) + 1. The diameter term places the extreme bar centrelines half a diameter inside the cover line. The ceiling keeps actual spacing at or below the entered maximum. Main mesh bars run along the length and are counted across the width.
Does the steel quantity include laps, wastage and development length?
No, except the extra length you enter per longitudinal bar in member mode. Laps, development length, chairs, cross-ties, starter bars, confinement zones and cutting waste must be added from the approved drawing.
Can I download the bar bending schedule in Excel?
Yes. Download BBS CSV and open it in Excel or another spreadsheet app. It contains the input dimensions, selected conventions, bar rows, step-by-step working, diameter summary and total weight. The export uses numeric results rather than spreadsheet formulas.