📊 Construction Tool
Bar Bending Schedule Calculator
Calculate cutting length, total length and steel weight for 7 bar shapes — IS 2502 / IS 13920 formulas. Export to Excel or print.
Project:
Drawing No.:
Prepared By:
Date:
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.
1
Steel Density
Density of steel
= 7850 kg/m³
(IS 800 standard value)
= 7850 kg/m³
(IS 800 standard value)
2
Bar Cross-section
Area = (π/4) × D²
D in metres
= π × D²(mm) / (4 × 10⁶)
D in metres
= π × D²(mm) / (4 × 10⁶)
3
Weight per Metre
W = Area × density
= (π/4) × (D/1000)² × 7850
per metre of bar
= (π/4) × (D/1000)² × 7850
per metre of bar
4
Simplify
π × 7850 / (4 × 10⁶)
≈ 1/162
∴ W = D² ÷ 162 kg/m
≈ 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.
1
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.
2
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.
3
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.
4
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⌉.
5
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.
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.
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.
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.