How to Read a Bar Bending Schedule (BBS): A Beginner's Guide
A bar bending schedule (BBS) is simply a table that lists every reinforcement bar in a concrete element. Once you know what each column means, it reads like an ingredients list for rebar — telling the fabricator exactly what to cut, how to bend it, and how many to make. This guide walks through each column.
The standard columns
| Column | What it tells you |
|---|---|
| Bar mark | A unique reference number for this bar within the drawing, so it can be identified on site. |
| Type / grade | The steel grade, e.g. B500B — the strength and ductility class of the bar. |
| Size | The nominal bar diameter in millimetres (10, 12, 16, 20…). |
| No. of bars | How many identical bars this mark represents (number of members × bars per member). |
| Shape code | The BS 8666 shape code that defines how the bar is bent (00 for straight, 51 for a stirrup, and so on). |
| Dimensions (A–F) | The individual leg lengths of the bent bar, matching the letters on that shape's diagram. |
| Cutting length | The total straight length the bar is cut to before bending, measured along its centre line. |
| Weight | The steel weight for this mark = cutting length × number of bars × mass per metre. |
How the pieces fit together
The shape code and the dimensions together define the bent shape. The cutting length is then calculated from those dimensions using the formula for that shape code in BS 8666:2020 Table 5. Finally, the weight comes from the cutting length and the bar's mass per metre. Sum the weights down the schedule and you have the total steel tonnage for the job.
A quick worked read
Say a row shows: mark 04, grade B500B, size 12, 20 no., shape code 00, A = 4500. That reads as twenty straight 12 mm bars, each cut to 4,500 mm. At 0.888 kg/m for a 12 mm bar, that's 4.5 m × 0.888 × 20 ≈ 79.9 kg for that mark.
Common questions
- Why is cutting length shorter than the sum of the legs? Because bending steel around a former shortens it slightly; the shape formula subtracts a bend allowance.
- What's the difference between "number of members" and "number of bars"? A member might be one beam; bars per member is how many of this mark go in each beam. Multiply them for the total.
Try it yourself
Skip the manual arithmetic — build the schedule in the free BS 8666:2020 calculator and export it.
Open the BBS calculator →Not a substitute for a checked, engineer-approved bending schedule.