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Free online BBS calculator (bar bending schedule calculator)
This free BBS calculator prepares a bar bending schedule for a building straight from the structural drawing. Enter each member and it gives the cutting length of every bar, the number of bars, the steel weight, the concrete quantity and the steel percentage. You can print the BBS or download it as an Excel sheet. It works for beams, columns, slabs, footings, staircases, lintels and retaining walls.
What is a bar bending schedule (BBS)?
BBS means Bar Bending Schedule. It is a table that lists every reinforcement bar in an RCC member: bar mark, diameter, shape, cutting length, number of bars, total length and weight. It is used to cut and bend steel on site, to order steel, to check the contractor’s bill and to control wastage.
BBS formulas used in this calculator
| Item | Formula |
|---|---|
| Cutting length of a bar | Sum of all legs − bend deductions |
| Bend deduction | 1d for 45°, 2d for 90°, 3d for 135° (d = bar diameter) |
| Cutting length of a stirrup | 2 × (a + b) + 2 × hook − 3 × 2d − 2 × 3d |
| Hook length of a stirrup | 10d, minimum 75 mm |
| Crank (bent-up) bar | Add 0.42 × H for each 45° crank, deduct 1d for each bend |
| Number of stirrups | (Length ÷ spacing) + 1 |
| Weight of steel bar | D² ÷ 162 kg per metre (D in mm) |
| Lap length | As on the drawing, entered as a multiple of bar diameter, for example 50d |
| Development length | Ld = φ × 0.87 fy ÷ (4 × τbd), as per IS 456 |
Example: cutting length of a stirrup
Beam 230 × 450 mm, clear cover 25 mm, 8 mm stirrups. a = 230 − 50 = 180 mm and b = 450 − 50 = 400 mm. Hook = 10 × 8 = 80 mm. Cutting length = 2 × (180 + 400) + 2 × 80 − 3 × 2 × 8 − 2 × 3 × 8 = 1224 mm. The calculator shows this working for every bar.
Unit weight of steel bars (D² ÷ 162)
| Bar diameter | Weight per metre | Weight of one 12 m bar |
|---|---|---|
| 8 mm | 0.395 kg | 4.74 kg |
| 10 mm | 0.617 kg | 7.41 kg |
| 12 mm | 0.889 kg | 10.67 kg |
| 16 mm | 1.580 kg | 18.96 kg |
| 20 mm | 2.469 kg | 29.63 kg |
| 25 mm | 3.858 kg | 46.30 kg |
| 32 mm | 6.321 kg | 75.85 kg |
For quick weights of any bar, use the TMT bar weight calculator in the site calculators.
BBS of beam, column, slab and footing
- BBS of beam: top bars, bottom bars, extra bars at supports, crank bars, side face bars and stirrups, with different stirrup spacing near the supports.
- BBS of column: vertical bars from the footing through every storey with laps, and rectangular, circular, inner or diamond ties.
- BBS of slab: main bars and distribution bars for one-way and two-way slabs, with cranked bars and extra top bars.
- BBS of footing: bottom mesh in both directions for pad, sloped, stepped, combined and strip footings, with the concrete quantity.
- BBS of staircase: waist slab main bars and distribution bars along the flights and landings.
How to make a bar bending schedule with this calculator
- Choose the member: beam, column, slab, footing, staircase, lintel or retaining wall.
- Choose the unit you want to type in: mm, metre or feet-inch.
- Enter the sizes and bars from the drawing. Tap the i beside any box to see a sketch of what to enter.
- Press Add. The form is then ready for the next member.
- Make the cutting plan and the bar bender’s sheet, then print the BBS or download the Excel sheet.
BBS questions and answers
What is the full form of BBS in civil engineering?
BBS stands for Bar Bending Schedule. It is a table that lists every reinforcement bar in an RCC member with its bar mark, diameter, shape, cutting length, number of bars, total length and weight. The bar bender cuts and bends steel from it, and the engineer uses it to order steel and check bills.
How do you calculate cutting length in a bar bending schedule?
Add the lengths of all the legs of the bar, then take off a bend deduction for each bend. This calculator deducts 1 bar diameter for a 45° bend, 2 for a 90° bend and 3 for a 135° bend by default, following common IS 2502 and SP 34 site practice. You can change these in the settings, and every bar shows its working.
What is the cutting length formula for a stirrup?
Cutting length of a rectangular stirrup = 2 × (a + b) + 2 × hook length − 3 × 2d − 2 × 3d, where a and b are the member width and depth less cover on both sides and d is the stirrup diameter. For a 230 × 450 mm beam with 25 mm cover and 8 mm stirrups: 2 × (180 + 400) + 2 × 80 − 48 − 48 = 1224 mm.
What is the formula for the weight of a steel bar?
Weight in kg per metre = D² ÷ 162, where D is the bar diameter in mm. A 12 mm bar weighs 12 × 12 ÷ 162 = 0.889 kg per metre, so one 12 m bar weighs about 10.67 kg.
What is the hook length of a stirrup?
The calculator takes the hook of a stirrup or tie as 10 times the bar diameter, with a minimum of 75 mm. For an 8 mm stirrup that is 80 mm for each hook.
What is bend deduction in BBS?
A bar stretches a little when it is bent, so the cut length is slightly less than the sum of its legs. The usual site deductions are 1d for a 45° bend, 2d for a 90° bend and 3d for a 135° bend, where d is the bar diameter.
How is the length of a crank (bent-up) bar calculated?
For a 45° crank, add 0.42 × H for each crank, where H is the crank height (member depth less covers and bars), and deduct 1d for each 45° bend.
How does the calculator handle lap length?
You enter the lap as a multiple of the bar diameter, for example 50d, as shown on your drawing. When a bar is longer than a standard 12 m bar, the calculator adds the laps needed by itself.
Which members can I prepare a BBS for?
Beams, columns, slabs, footings (pad, sloped, stepped, combined and strip), staircases, lintels with chajja, and retaining walls.
Can I add more than one beam or column?
Yes. Add as many members as the drawing has, one after another, each with its own mark such as B1, B2 and B3. Use “No. of similar” for identical members. Every member in the list can be changed, copied or removed.
Can I download the bar bending schedule in Excel?
Yes. The Excel file has four sheets: the bar bending schedule, a summary of steel and concrete, the workings for every bar, and a bar bender’s sheet with a picture of each bar and its sizes after bending. You can also print it.
Does it help with ordering and cutting steel?
Yes. It adds wastage for ordering, and the cutting plan shows how many standard bars to buy and how to cut them with the least scrap.
Is this BBS calculator free?
Yes. It is free, needs no login or app, and works on a phone or a computer. You can type sizes in mm, metres or feet-inches. The members you add are kept in your own browser, and nothing is sent to the website.
Always check leg, lap and anchorage lengths against the structural drawing and IS 456 or IS 13920 before cutting steel.