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If you work on a construction site, you have heard the term BBS. It tells the team exactly how many steel bars to cut, how long each one should be, and how much steel to order. A mistake here means wasted steel, wasted money, and delays.

What Is a Bar Bending Schedule?

A Bar Bending Schedule is a table that lists every steel bar in a structure. For each bar, it gives the bar mark, shape, diameter, number of bars, cutting length, and total weight.

Think of it as a shopping and cutting list for steel.

Who Uses a BBS?

• Site engineer: to check the work against the drawing
• Steel fixer: to know which bars to cut and bend
• Contractor: to order the right amount of steel
• Quantity surveyor: to estimate cost and prepare bills
• Inspector: to confirm the steel matches the design

What You Need Before You Start

• The structural drawing with bar details
• Cover, spacing, and bar diameters from the drawing
• Excel on your laptop
• The four formulas below

The 4 Formulas You Need

1. Number of stirrups

Number of stirrups = (Length ÷ Spacing) + 1, always rounded up

2. Cutting length of a bent bar

Cutting length = Length before deduction − (Number of bends × Deduction × Bar diameter)

Why deduct? When a bar is bent, its length measured along the outside corner is longer than the length actually needed. The deduction fixes that.

3. Stirrup length

Length = 2(A + B) + 24 × diameter (for 135° hooks)

Here, A = beam width − 2 × cover, and B = beam depth − 2 × cover.

4. Weight of steel

Unit weight (kg/m) = D² ÷ 162, where D is in mm

Weight = Total length (m) × Unit weight

Worked Example: RCC Beam

Here is the beam used in the sample sheet:

• Beam size: 300 × 450 mm
• Beam length: 5,500 mm
• Number of beams: 4
• Clear cover: 25 mm
• Stirrups: 8 mm bars at 150 mm c/c

Reinforcement used:

Step 1: Count the stirrups

5,500 ÷ 150 = 36.67, and 36.67 + 1 = 37.67, which rounds up to 38 stirrups per beam.

Step 2: Find the stirrup cutting length

A = 300 − 50 = 250 mm and B = 450 − 50 = 400 mm

Length = 2 × (250 + 400) + 24 × 8 = 1,492 mm

Step 3: Find the cutting length of the bottom bars

Length before deduction = 5,500 − 50 + (2 × 12 × 16) = 5,834 mm

Two 90° bends: deduction = 2 × 2 × 16 = 64 mm

Cutting length = 5,834 − 64 = 5,770 mm

Step 4: Find the weight

16 mm bar: 16² ÷ 162 = 1.58 kg/m

Total length = 5.77 m × 12 bars = 69.24 m

Weight = 69.24 × 1.58 ≈ 109.4 kg

Step 5: Add everything up

The sheet does this for you. For these 4 beams, the total comes to about 261 kg of steel. Adding 3% wastage, you should order about 269 kg.

How to Make This in Excel: Quick Steps

1. Create the columns: Bar Mark, Description, Dia, Nos per beam, Total nos, Length, Bends, Deduction, Cutting length, Total length, Unit weight, Weight.
2. Put your inputs in one place. Beam length, width, depth, cover, and spacing go on a separate sheet. Then every formula picks them up, and you never retype numbers.
3. Use formulas, not typed answers. For example, the stirrup count is =ROUNDUP(Length/Spacing+1,0).
4. Add a summary by diameter. Use SUMIF to total the weight of each bar size. This is what you give your supplier.
5. Add a check. Compare the summary total with the BBS total. If they differ, a bar size is missing.

5 Common BBS Mistakes

1. Rounding down the stirrup count. Always round up.
2. Forgetting bend deductions. Bars come out too long.
3. Mixing up inside and outside stirrup dimensions. Check the cover.
4. Skipping wastage. You will run short on site.
5. Copying values from a sample without checking the drawing. Every project has its own detailing.

Tips for 2026

• Keep one master template and copy it for each beam, column, and slab.
• Name your files clearly, such as BBS_Floor2_Beams_V2.xlsx.
• Use Excel’s colour coding, with blue for inputs and black for formulas, so no one overwrites a formula by accident.
• Always follow your drawing and local code (for example, IS 456 and IS 2502 in India).

FAQs

What is the unit weight formula for steel bars?

D² ÷ 162 kg per metre, where D is the diameter in mm.

Why do we add 1 when counting stirrups?

Because stirrups are placed at both ends of the length. Count the gaps, then add one more stirrup.

Is Excel good enough for BBS?

Yes, for most site and estimation work. Specialised detailing software helps on very large projects, but Excel is quick, cheap, and easy to check.

How much wastage should I add?

Many sites use about 3–5%. Follow your company or project rules.

Final Thoughts

A good BBS saves steel, time, and arguments on site. Start with the sample sheet, change the yellow cells to match your drawing, and check the totals. Once you’re comfortable, build the same type of sheet for columns, slabs, and footings.