Bar Bending Schedule of Slab: Worked Example
A slab bar bending schedule lists every bar by mark, direction, diameter, shape, count, cutting length and weight. In this worked 3,050 × 6,050 mm panel, the bottom mesh is 41 bars of 10 mm at 3,000 mm plus 16 bars of 8 mm at 6,000 mm: 57 bars, 113.85 kg.
A worked quantity example, not a reinforcement design. Weights use D²/162 kg/m; link bends use site approximations explained below. Reviewed 20 October 2026.
One workbook with slab, beam, column and footing sheets. Change any dimension and the counts, cut lengths, weights and diameter totals recalculate. The PDF prints these four examples.
Worked slab: dimensions and scope
One 3,050 × 6,050 × 150 mm slab panel, supported on its two long sides. The table covers its two straight bottom-mesh marks only. Support anchorage, top bars, opening bars and chairs are excluded.
S1 runs along the 3,050 mm short direction and is counted across the 6,050 mm direction. S2 runs along the long direction and sits on top of S1. Bottom cover is 25 mm to S1; edge cover is 25 mm to the steel surface. Thickness sets the section but does not change these straight plan lengths.
| Input | Value | Unit |
|---|---|---|
| Short overall panel dimension | 3,050 | mm |
| Long overall panel dimension | 6,050 | mm |
| Slab thickness | 150 | mm |
| Edge and bottom cover | 25 | mm |
| S1 main bar diameter | 10 | mm |
| S1 maximum spacing | 150 | mm |
| S2 distribution diameter | 8 | mm |
| S2 maximum spacing | 200 | mm |
Cutting lengths and bar counts, step by step
Each line puts the inputs above into one formula. ROUNDUP(x, 0) rounds up to a whole number and MAX takes the larger value. Bar counts include both end bars.
1. S1 straight cutting length
3050 − 2 × 25 = 3,000 mm
2. S1 first-to-last centre distance
6050 − 2 × 25 − 10 = 5,990 mm
3. S1 spaces, rounded up
ROUNDUP(5990 ÷ 150,0) = 40 spaces
4. S1 bar count
40 + 1 = 41 bars
5. S2 straight cutting length
6050 − 2 × 25 = 6,000 mm
6. S2 first-to-last centre distance
3050 − 2 × 25 − 8 = 2,992 mm
7. S2 spaces, rounded up
ROUNDUP(2992 ÷ 200,0) = 15 spaces
8. S2 bar count
15 + 1 = 16 bars
Full BBS table for the stated example
The slab example totals 113.85 kg from 57 bars. Total length = count × cutting length ÷ 1,000; unit weight = D²/162 kg/m; weight = total metres × unit weight.
| Bar mark / position | Shape | Dia (mm) | No. of bars | Cut length (mm) | Total length (m) | D²/162 (kg/m) | Weight (kg) |
|---|---|---|---|---|---|---|---|
| S1Bottom main, short direction | Straight | 10 | 41 | 3,000 | 123.000 | 0.617284 | 75.93 |
| S2Bottom distribution, long direction | Straight | 8 | 16 | 6,000 | 96.000 | 0.395062 | 37.93 |
| Example subtotal | 57 | 219.000 | 113.85 | ||||
S1: 41 × 3,000 ÷ 1,000 = 123.000 m; 123.000 × 10² ÷ 162 ≈ 75.925926 kg → 75.93 kg.
S2: 16 × 6,000 ÷ 1,000 = 96.000 m; 96.000 × 8² ÷ 162 ≈ 37.925926 kg → 37.93 kg.
Steel summary by diameter
| Diameter | Pieces | Total metres | Weight (kg) |
|---|---|---|---|
| 8 mm | 16 | 96.000 | 37.93 |
| 10 mm | 41 | 123.000 | 75.93 |
Unrounded row weights are added first, then the 113.85 kg total is rounded, so displayed rows can differ by 0.01 kg. Cutting waste is not included.
IS code checks and conventions used
The bend deductions and hook length below are site approximations; IS 2502, SP 34 and IS 13920 govern the approved bar shapes. The examples use the same marks and quantities as the BBS format and IS-code guide. A bar mark is only an identifier: IS 2502 clause 3.1 and SP 34 section 5 call for a dimensioned shape for each bar.
Dimensions
All inputs and cut lengths are in mm. Link dimensions are outside-to-outside. Cover is measured to the outer steel surface.
Do not put centreline dimensions into the outside-dimension link shortcut.
Bend deductions
Site approximations: 45° = 1d, 90° = 2d, 135° = 3d. Each closed link here has three 90° corners and two 135° hooks.
IS 2502 and SP 34 dimension each shape with its own allowances; neither gives one angle-only deduction table. Bend radius and steel type change the true value.
Hook extension / allowance
H = max(10d, 75 mm) per hook; for an 8 mm link, H = 80 mm.
10d (at least 75 mm) is the IS 13920:1993 hook extension, clauses 6.3.1 and 7.3.1. The 2017 amendment to IS 13920:2016 uses 8d (at least 75 mm). We keep 10d to match our BBS guide; use the edition your project specifies.
Approximate link length
2(a + b) + 2H − [3(2d) + 2(3d)], rounded up to the next 25 mm.
A site estimating shortcut, not a bend allowance from IS 2502. Fabricate to the approved shape and bend radius.
Bar counts
Ceiling(first-to-last centre distance / maximum spacing) + 1.
Both end bars are included. For a mesh, centre distance = overall size across the bars − 2 × cover − bar diameter. Count a bar on a shared zone boundary once.
Weight
Total length × D²/162 kg/m, kept at full precision until display.
A close approximation: 12 mm gives 0.888889 kg/m against 0.888 kg/m in IS 1786 Table 1. Bill on the basis your contract states.
Rounding and scope
Bent lengths round up to the next 25 mm; the straight lengths here already land on 25 mm. Weights show 2 decimals.
IS 2502 clause 5.1.1 and SP 34 clause 13.3.3.1 take the rounding excess into a portion named on the schedule. Waste, stock-length optimisation and bars not shown here are extra.
Sources checked
- IS 2502:1963 — clauses 3.1, 5.1.1 and Tables II–IX
Dimensioned shapes, allowances and cutting-length increments.
- SP 34:1987 — section 5 and clause 13.3.3.1
Bar marks, member schedules, sketches and the 25 mm scheduling increment.
- IS 13920:1993 — clauses 6.3.1 and 7.3.1
135° hook extension for beam and column hoops: 10d, at least 75 mm.
- IS 13920:2016, Amendment 1 (September 2017)
Reproduced BIS amendment (third-party copy): 8d, at least 75 mm, in beam clause 6.3.1(a) and column clause 7.4.1. Check the edition your project specifies.
- IS 1786:2008 — Table 1
Nominal mass per metre; differs slightly from the D²/162 approximation.
- IS 456:2000 — clauses 26.2 and 26.4
Development, laps and nominal cover; use the approved design values.
Common slab BBS mistakes
Counting main bars along their length
S1 is 3,000 mm long but its 41 bars are counted across the long panel dimension.
Using thickness as the crank rise
This mesh has no cranks. For a bent-up bar, derive the vertical centreline rise from the actual layer detail.
Treating the mesh total as all slab steel
Read support sections, openings, top bars and chairs before adding the reinforcement BOQ quantity.
Using 40 bars because 5,990/150 is about 40
There are 40 spaces and 41 endpoint-inclusive bars. Actual equal spacing is 5,990/40 = 149.75 mm.
Use a checked BBS in your BOQ and billing
Carry BBS kilograms into the reinforcement BOQ item only after every bar on the drawings is accounted for. Keep the member, floor or pour, drawing revision, shape and checker with each schedule. For BBS from your full drawing set, get a BOQ from drawings below; for monthly BBS with measurement sheets and RA bills, use the construction billing desk.
FAQs: BBS of slab
How do you calculate a slab BBS?
Separate each direction and layer. Read diameters and shapes from the drawing, count across the perpendicular centre distance, find each cutting length, then multiply count × length in metres × D²/162.
What is the cutting length of S1 in this slab?
3,050 − 2 × 25 = 3,000 mm for the straight bar inside the panel outline. It excludes any support anchorage.
Why are there 41 main bars?
The centre distance is 6,050 − 50 − 10 = 5,990 mm. Round 5,990/150 up to 40 spaces, then add one endpoint bar: 41.
Are distribution bars counted the same way?
Yes, across the other direction: 3,050 − 50 − 8 = 2,992 mm. Ceiling(2,992/200) + 1 gives 16 bars.
Does the slab thickness change these cutting lengths?
Not for the two straight mesh marks shown. Thickness matters for layer levels, effective depth, cranks, chairs and structural design.
Should every alternate slab bar be cranked?
Only where the drawing shows cranked bars. A 45° crank adds about 0.42 × the vertical centreline rise of the crank, not 0.42 × the bar diameter. Site formulas then deduct 1d for each 45° bend.
Can this slab BBS be used for procurement?
Not on its own. It is the bottom mesh only. Add every other bar on the drawing, check anchorage and revisions, then add a separate allowance for stock lengths and cutting waste.