BBS of Footing: Bar Bending Schedule Example
A footing BBS lists the bottom mesh, starters and any other bars by mark, each with shape, count, cutting length and weight. In this worked 2,100 × 2,100 mm isolated footing, the bottom mesh is 15 + 15 bars of 12 mm at 2,000 mm each: 30 bars, 53.33 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 footing: dimensions and scope
One 2,100 × 2,100 × 450 mm isolated footing with 50 mm edge and bottom cover. The bottom mesh is straight 12 mm bars at 150 mm maximum spacing both ways. Only these two bottom-mesh marks are included.
F1 runs in X as the lower layer; F2 runs in Y directly on top of it. Edge cover is measured to each bar's surface. Footing depth sets the section but does not enter these straight cutting lengths. Column starters, chairs, top steel and any bent-up ends are excluded.
| Input | Value | Unit |
|---|---|---|
| Footing overall X dimension | 2,100 | mm |
| Footing overall Y dimension | 2,100 | mm |
| Footing thickness | 450 | mm |
| Edge and bottom cover | 50 | mm |
| F1 X-bar diameter | 12 | mm |
| F1 maximum spacing | 150 | mm |
| F2 Y-bar diameter | 12 | mm |
| F2 maximum spacing | 150 | 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. F1 straight cutting length
2100 − 2 × 50 = 2,000 mm
2. F1 centres across Y
2100 − 2 × 50 − 12 = 1,988 mm
3. F1 spaces, rounded up
ROUNDUP(1988 ÷ 150,0) = 14 spaces
4. F1 bar count
14 + 1 = 15 bars
5. F2 straight cutting length
2100 − 2 × 50 = 2,000 mm
6. F2 centres across X
2100 − 2 × 50 − 12 = 1,988 mm
7. F2 spaces, rounded up
ROUNDUP(1988 ÷ 150,0) = 14 spaces
8. F2 bar count
14 + 1 = 15 bars
Full BBS table for the stated example
The footing example totals 53.33 kg from 30 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) |
|---|---|---|---|---|---|---|---|
| F1Bottom mesh, X direction | Straight | 12 | 15 | 2,000 | 30.000 | 0.888889 | 26.67 |
| F2Bottom mesh, Y direction | Straight | 12 | 15 | 2,000 | 30.000 | 0.888889 | 26.67 |
| Example subtotal | 30 | 60.000 | 53.33 | ||||
F1: 15 × 2,000 ÷ 1,000 = 30.000 m; 30.000 × 12² ÷ 162 ≈ 26.666667 kg → 26.67 kg.
F2: 15 × 2,000 ÷ 1,000 = 30.000 m; 30.000 × 12² ÷ 162 ≈ 26.666667 kg → 26.67 kg.
Steel summary by diameter
| Diameter | Pieces | Total metres | Weight (kg) |
|---|---|---|---|
| 12 mm | 30 | 60.000 | 53.33 |
Unrounded row weights are added first, then the 53.33 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 footing BBS mistakes
Counting across the bar's own direction
F1 length comes from X; its count comes from Y. This distinction matters for rectangular footings.
Omitting the final bar at the far edge
Ceiling(1,988/150) is 14 spaces, giving 15 bars, not 14.
Automatically adding hooks to every footing bar
These bars are explicitly straight. Use bent ends only where the engineer's detail requires them.
Calling 53.33 kg the complete foundation steel
Add starters, chairs, top steel and connected pedestals separately before procuring or billing.
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 footing
How is BBS of an isolated footing calculated?
Schedule X and Y bars separately. Use each bar's run for cutting length and the perpendicular centre distance for its count, then sum metres × D²/162.
What is the cutting length for this footing?
Both straight mesh marks are 2,100 − 2 × 50 = 2,000 mm long. No bent end or anchorage extension is assumed.
How many bars are provided each way?
The centre distance is 2,100 − 100 − 12 = 1,988 mm. Ceiling(1,988/150) + 1 gives 15 bars per direction, or 30 in the mesh.
Is 50 mm cover suitable for every footing?
50 mm is the IS 456 minimum for footings (clause 26.4.2.2). Exposure conditions can call for more, so use the cover on your drawings.
Why does the total differ from two displayed row weights?
Each direction weighs 26.666666… kg, displayed as 26.67 kg. Add the unrounded values first: 53.333333… kg, displayed as 53.33 kg.
Does this include column starter bars?
No. Starters need their own shape, embedded length, bends, projection and lap allocation from the approved footing/column details.
How does a rectangular footing change the BBS?
Use different X and Y dimensions. F1 and F2 can then have different cut lengths, counts and weights even when diameter and maximum spacing are the same.