Bar Bending Schedule (BBS) Quantity Calculator

• Unit weight (kg/m) = d² / 162 where d is bar diameter in mm.
• Row weight (kg) = Qty × CutLength(m) × UnitWeight(kg/m).
• Steel incl. wastage = Steel × (1 + Wastage%/100).
• Binding wire (kg) = Steel incl. wastage × (Wire%/100).
• Cost = Steel incl. wastage × RatePerKg (optional).

1. Add each reinforcement item as a new row and set its mark.
2. Select the bar shape and enter diameter and quantity.
3. Choose Direct to type cutting length in mm, or By Shape to enter dimensions.
4. Add hook and lap lengths when needed, then set wastage and wire percentages.
5. Click Calculate to view the itemized schedule and totals above.
6. Use Download CSV or Download PDF for documentation and billing.

Professional Notes on BBS Quantity Planning

1) Why a BBS improves control

A Bar Bending Schedule organizes reinforcement into marked items with diameter, shape, quantity, and cutting length. When the schedule is consistent, procurement becomes predictable and fabrication mistakes reduce. The calculator turns each item into total length and weight.

2) Unit weight and quick checks

On most sites, unit weight is estimated using kg per meter equals diameter squared divided by 162, with diameter in millimeters. For example, a 10 mm bar is about 0.617 kg/m and a 16 mm bar is about 1.580 kg/m. Quick checks like these support store ledgers and delivery reconciliation.

3) Cutting length logic for common shapes

Straight bars use direct cutting length. L-bars add two legs plus one bend allowance. U-bars add the base, two legs, and two bends. Stirrups often use two times (A plus B), add hooks, then add bend allowances. Circular rings can be approximated with pi times diameter plus lap.

4) Bend allowance choices

Bend allowance varies by pin diameter and detailing standards. A quick estimate is 2d for a 90 degree bend and 3d for a 135 degree bend, where d is bar diameter. For more detail, the arc method uses the bend diameter factor.

5) Laps, hooks, and anchorage

Laps and hooks add steel to every bar. A small lap repeated across many bars increases weight noticeably. Enter lap length for splices and hook length for ties, then confirm values against drawings and bar marks.

6) Wastage and handling losses

Wastage covers cutting losses, end pieces, rework, and site handling. Many projects use 2 to 6 percent depending on complexity and reuse of offcuts. The calculator applies wastage to total steel weight for a practical procurement buffer. For high-rise and congested zones, review wastage monthly regularly based on actual cutting returns.

7) Binding wire and productivity

Binding wire is often estimated as 1 to 2 percent of steel weight, but it can rise with dense reinforcement and close tie spacing. Tracking wire alongside steel helps prevent fixing delays and improves future estimating accuracy.

8) Using outputs for procurement and billing

Use the itemized table for cutting lists and shop orders, and use summary totals for purchase requests, reconciliation, and payment measurement. If you enter a rate per kilogram, the tool provides a fast cost estimate. CSV supports analysis, while PDF supports quick approvals. Keep exported files with revision dates to match drawing updates.

FAQs

1) What is a BBS in construction?

A BBS is a structured list of reinforcement bars showing mark, diameter, shape, quantity, and cutting length. It supports fabrication, ordering, and reconciliation by converting drawings into measurable steel quantities.

2) Which unit weight formula does this calculator use?

It uses the common site approximation: unit weight in kg/m equals diameter squared divided by 162, with diameter in millimeters. This is widely used for quick estimating and checking.

3) Should I enter lengths in millimeters or meters?

Enter bar dimensions and cutting length in millimeters. The calculator automatically converts to meters for weight calculations and reporting, keeping inputs consistent with typical drawing dimensions.

4) How do lap lengths affect the total quantity?

Lap length is added to the cutting length of each affected bar. When quantity is high, even small laps can increase total weight significantly, so always use lap values specified in your detailing notes.

5) What wastage percentage should I use?

Many projects start with 2 to 6 percent. Higher values may be needed for complex shapes, congestion, or frequent design changes. Use past site data when available and adjust after reconciliation.

6) Can I calculate stirrups and ties with hooks?

Yes. Select a stirrup shape, enter A and B dimensions, and add hook length. The calculator includes bend allowance and hooks to estimate cutting length and weight for each row.

7) What do the CSV and PDF exports include?

Exports include the itemized schedule with mark, shape, diameter, quantity, cutting length, unit weight, and row weight, plus a summary of totals such as steel weight, wastage, wire estimate, and cost.