What is a Bar Bending Schedule (BBS)?

A Bar Bending Schedule (BBS) is a detailed document prepared by structural engineers listing every reinforcement bar in a concrete structure with its shape, diameter, cutting length, number of bars, and weight. It is used for material procurement, cutting and bending at the fabrication yard, and billing purposes.

How is cutting length calculated for a stirrup?

For a rectangular stirrup of dimensions A×B: Cutting Length = 2(A+B) − 8d + hook allowance. IS 2502 uses 90° hooks (9d each side), giving +18d. IS 13920 uses 135° seismic hooks (12d each side), giving +24d. The −8d accounts for four 90° bend deductions (2d each).

What is the D²/162 formula?

The D²/162 formula calculates the weight of steel reinforcement bars in kg per metre run. It is derived from the density of steel (7850 kg/m³) and the cross-sectional area of the bar. Weight per metre = (π/4) × D² × 7850 / 10⁶ ≈ D²/162 where D is diameter in mm.

What is the difference between IS 2502 and IS 13920 hooks?

IS 2502 specifies standard 90° hooks with a minimum extension of 4d beyond the bend, giving a total hook allowance of 9d. IS 13920 (seismic detailing) requires 135° hooks with a minimum extension of 10d beyond the bend, giving a total hook allowance of 12d. Use IS 13920 hooks for stirrups and ties in earthquake-resistant construction in seismic zones III, IV and V.

How much wastage should I add for steel?

A wastage allowance of 3–5% is standard for straightforward reinforcement work. Add 5–8% for complex structures with many short bars and offcuts. The default in this calculator is 5%, which is widely accepted for estimation purposes in India.

What is the standard length of steel bars in India?

Steel reinforcement bars (TMT/Fe 500) are supplied in standard lengths of 12 metres in India. Some suppliers offer 9 m and 11 m lengths for smaller diameters. The Bars to Order column in this calculator divides total length by the standard bar length and rounds up to the next whole number.

How do I calculate laps in a BBS?

Lap length as per IS 456 is typically 50 times the bar diameter (50d). In this calculator, enter the number of laps per bar in the No. Laps column. The lap length (50d per lap) is added to the cutting length before multiplying by the number of bars and members.

What is cover and why is it deducted in BBS?

Cover (or clear cover) is the distance between the outer face of concrete and the nearest reinforcement bar surface. It protects steel from corrosion and fire. In a BBS, cover is deducted from each end of the bar (2×cover total) to find the cutting length. Typical covers are 25 mm for columns/beams, 40 mm for footings, and 50 mm for foundations in contact with soil.

BBS kaise banate hain? (Hindi)

BBS banane ke liye: 1) Structural drawing se sabhi bar marks, shape, diameter aur dimensions note karein. 2) Cutting length formula se har bar ki cutting length calculate karein (IS 2502 ya IS 13920 as applicable). 3) Total length = Cutting length × No. of bars × No. of members. 4) Weight = Total length × D²/162. 5) Bars to order = Total length ÷ Standard bar length (12 m). Upar diye calculator mein yeh sab automatic calculate hota hai.

Can this BBS calculator be used for UAE/international projects?

Yes. The D²/162 weight formula is universal. For UAE/GCC projects, use the IS 13920 hook setting (135°) which matches ACI 318 seismic hook requirements. Adjust cover to match BS 8666 or ASTM A615 project specifications. Standard bar length can be changed from 12 m to 6 m (common in UAE) using the Std Bar Length input.

Bar Bending Schedule Calculator

Bar Bending Schedule Calculator — Free BBS Tool with IS 2502 Formulas

Project:

Drawing No.:

Prepared By:

Date:

Hook Std:

Cover (mm):

Std Bar (m):

Rate ₹/kg:

Wastage %:

Schedule

#	Bar Mark	Member	Shape	Dia	Members	Bars/Mbr	Dim A (mm)	Dim B (mm)	Dim C (mm)	Laps	Cut. Length (m)	Total Length (m)	Bars to Order	Weight (kg)

Total Steel net weight, kg — D²/162 formula

—

With Wastage including wastage allowance

—

Estimated Cost at ₹/kg rate entered above

—

Bar Diameters Used distinct dia values in schedule

—

Bar Bending Schedule Formula — D²/162 Explained

Every Bar Bending Schedule relies on two core calculations: the cutting length formula for each bar shape (from IS 2502) and the D²/162 formula for converting bar length into weight in kilograms. Understanding these derivations helps engineers verify their schedules and catch errors before steel reaches the fabrication yard.

Steel Density

Density of steel
= 7850 kg/m³
(IS 800 standard value)

Bar Cross-section

Area = (π/4) × D²
D in metres
= π × D²(mm) / (4 × 10⁶)

Weight per Metre

W = Area × density
= (π/4) × (D/1000)² × 7850
per metre of bar

Simplify

π × 7850 / (4 × 10⁶)
≈ 1/162
∴ W = D² ÷ 162 kg/m

D²/162 — Universal Steel Weight Formula

Weight (kg/m) = D² ÷ 162

D = diameter in mm | Total weight = (D² ÷ 162) × Total Length (m)

Worked Example — Rectangular Stirrup (IS 2502)

Given: Rectangular stirrup, A = 300 mm, B = 450 mm, dia = 10 mm, IS 2502 (90° hook), cover = 25 mm

Bend deduction (4 × 90° corners): 4 × 2d = 4 × 20 = 80 mm → 8d = 80 mm

Hook allowance (IS 2502, both ends): 2 × 9d = 2 × 90 = 180 mm

Perimeter: 2 × (300 + 450) = 1500 mm

Cover deduction: 2 × 25 = 50 mm

Cutting length = 1500 − 80 + 180 − 50 = 1550 mm = 1.550 m

Weight per bar = 1.550 × (10² ÷ 162) = 1.550 × 0.617 = 0.957 kg

Steel Bar Weight Chart — 6mm to 32mm (IS 1786)

Reference table for TMT bar weight per metre and per standard 12 m length. Values calculated using the D²/162 formula, which matches tabulated values in IS 1786 and SP 34.

Diameter (mm)	Weight per metre (kg/m)	Weight per 12 m bar (kg)
6 mm	0.222	2.67
8 mm	0.395	4.74
10 mm	0.617	7.40
12 mm	0.888	10.66
16 mm	1.580	18.96
20 mm	2.469	29.63
25 mm	3.858	46.30
32 mm	6.321	75.85

Hook allowances and bend deductions to apply when calculating cutting lengths:

Diameter (mm)	IS 2502 Hook (9d) mm	IS 13920 Hook (12d) mm	90° Bend Deduction (2d) mm
6 mm	54	72	12
8 mm	72	96	16
10 mm	90	120	20
12 mm	108	144	24
16 mm	144	192	32
20 mm	180	240	40
25 mm	225	300	50
32 mm	288	384	64

Bend Angle	Deduction (multiples of d)	Example: 10 mm bar
45°	1d	10 mm
90°	2d	20 mm
135°	3d	30 mm
180°	4d	40 mm

How to Prepare a Bar Bending Schedule — 5 Steps

A properly prepared BBS reduces material wastage, speeds up fabrication and provides a clear audit trail for quantity surveyors and site engineers.

Read the Drawing

Identify all bar marks (e.g., T1, B1, S1), shapes, diameters, spacing and dimensions from the reinforcement drawing. Note the number of members (e.g., number of beams) and bars per member.

Set Global Parameters

Decide on the hook standard (IS 2502 for general use, IS 13920 for seismic zones III–V), nominal cover per IS 456, standard bar length (12 m), and material rate per kg for cost estimation.

Calculate Cutting Lengths

Apply the appropriate IS 2502 formula for each bar shape. Deduct 2 × cover from the overall dimension. Add hook allowances. Deduct bend allowances. Check each bar mark independently.

Calculate Weight

Total length = cutting length × no. of bars × no. of members + lap lengths. Weight (kg) = total length × D²/162. Bars to order = ⌈total length ÷ standard bar length⌉.

Review and Submit

Cross-check with the abstract of reinforcement in the BOQ. Add 3–5% wastage for cutting losses. Export to Excel or print for site and procurement teams. Get sign-off from the structural engineer.

Wastage Guidelines (IS 456)

Standard reinforcement work: 3–5%
Complex shapes / many short bars: 5–8%
Site cutting (no pre-fabrication): 8–10%
Add extra for couplers or threaded ends: +1–2%
Default in this calculator: 5%

IS Codes Reference

IS 2502:1963 — Code of practice for bending and fixing of bars for concrete reinforcement
IS 13920:2016 — Ductile detailing for seismic resistance
IS 456:2000 — Plain and reinforced concrete (code of practice)
IS 1786:2008 — High strength deformed steel bars (TMT)
SP 34:1987 — Handbook on concrete reinforcement and detailing

Frequently Asked Questions

A Bar Bending Schedule (BBS) is a detailed document prepared by structural engineers that lists every reinforcement bar in a concrete structure with its bar mark, shape, diameter, cutting length, number of bars, and total weight. It is used for material procurement, cutting and bending at the fabrication yard, and billing purposes. A well-prepared BBS reduces steel wastage, speeds up site execution, and provides a clear audit trail for quantity surveyors.

For a rectangular stirrup of dimensions A × B:

Cutting Length = 2(A + B) − 8d + Hook Allowance − 2 × Cover

The −8d accounts for four 90° bend deductions (2d each corner). IS 2502 uses 90° hooks with allowance 2 × 9d = 18d added. IS 13920 uses 135° seismic hooks with allowance 2 × 12d = 24d added. Cover is deducted from both ends. For a 300×450 mm stirrup in 10 mm dia with IS 2502 and 25 mm cover: CL = 2(300+450) − 80 + 180 − 50 = 1550 mm.

The D²/162 formula calculates the weight of a steel bar in kg per metre of length. It is derived from first principles:

Weight per metre = (π/4) × (D/1000)² × 7850 kg/m³
= π × 7850 / (4 × 10⁶) × D²
≈ D² / 162 kg/m

where D is the bar diameter in mm and 7850 kg/m³ is the density of steel per IS 800. Total weight = (D²/162) × Total Length in metres.

IS 2502 specifies standard 90° hooks with a minimum straight extension of 4d beyond the bend radius, giving a total hook allowance of approximately 9d. IS 13920 (seismic detailing) requires 135° hooks with a minimum straight extension of 10d beyond the bend, giving a total hook allowance of 12d. The 135° hook provides superior anchorage and confinement in earthquake-resistant joints. Use IS 13920 hooks for all stirrups and ties in structures located in seismic zones III, IV and V as per IS 1893.

A wastage allowance of 3–5% is standard for straightforward reinforcement work where bars are pre-fabricated off-site and the BBS is well-prepared. Increase to 5–8% for complex structures with many different bar lengths, short offcuts, or when cutting is done on-site. The default in this calculator is 5%, which is widely accepted for estimation and tendering purposes in India. Note that the wastage % applies to the total weight after all cutting lengths are calculated.

Steel reinforcement bars (TMT Fe 500 / Fe 500D) are supplied in standard lengths of 12 metres in India, as per IS 1786:2008. Some suppliers also offer 9 m and 11.5 m lengths for smaller diameters (6–10 mm) for easier transportation. The Bars to Order column in this calculator divides the total required length by the standard bar length (default 12 m) and rounds up to the nearest whole number. You can change the standard bar length in the Settings Bar above to match your supplier’s stock length.

Lap length as per IS 456:2000 is typically 50 times the bar diameter (50d) for tension laps in Fe 500 steel in M20 concrete. This is the minimum — check the structural drawing notes for the specified lap length as it can be 40d, 50d or 60d depending on concrete grade and bar position. In this calculator, enter the number of laps per bar in the No. Laps column. The lap addition = No. of Laps × 50d per bar, which is added to the cutting length before multiplying by the number of bars and members.

Cover (or clear cover) is the distance between the outer face of concrete and the nearest surface of a reinforcement bar. It protects steel from corrosion, fire, and carbonation. In a BBS, cover is deducted from both ends of the bar (i.e., 2 × cover is subtracted from the overall bar dimension) to find the net cutting length. Typical minimum covers per IS 456: columns and beams = 25–40 mm; slabs = 20–25 mm; footings = 40–50 mm; members exposed to soil or water = 50 mm. The cover setting in the calculator’s Settings Bar applies this deduction to all rows.

BBS (Bar Bending Schedule) banane ke liye yeh steps follow karein:

1. Drawing padhein — Structural drawing se sabhi bar marks, shape, diameter aur dimensions note karein.
2. Global settings set karein — Hook standard (IS 2502 ya IS 13920), cover (mm), standard bar length (12 m) aur rate (₹/kg) set karein.
3. Cutting length calculate karein — Har bar ke liye IS 2502 ka formula use karein. Cover deduct karein, hook allowance add karein, bend deduction hatayein.
4. Total length aur weight nikaalein — Total length = CL × no. of bars × no. of members. Weight = Total length × D²/162.
5. Export ya print karein — Excel export ya A4 print option use karein site aur procurement ke liye.

Upar diye calculator mein yeh sab automatic calculate hota hai — sirf dimensions enter karein.

Yes. The D²/162 weight formula is universal and matches values in BS 8666 and ACI 318 reference tables. For UAE/GCC projects: (1) Use the IS 13920 hook setting (135°) which matches ACI 318-19 seismic hook requirements. (2) Adjust nominal cover to match project specification (BS 8500 exposure class or ACI 318 requirements). (3) Change the standard bar length from 12 m to 6 m (common stock length in UAE) or 9 m as required. The Excel export includes all project header information suitable for submission to MEP contractors and quantity surveying teams.