How to Read a Bar Bending Schedule: Bar Mark, Shape Code, Diameter, Length, and Weight

A bar bending schedule is the document that translates a structural engineer’s reinforcement drawings into a fabrication instruction list. Every row in the schedule corresponds to a distinct bar type in a structural element, and every column carries a specific piece of information the fabricator needs to cut and bend the bar correctly. Misreading even a single column — confusing the cutting length with the overall length, or transposing a bar mark — can result in bars that won’t fit, wasted material, or, in the worst case, structural non-compliance.

This guide explains how to read a bar bending schedule column by column, referencing the BS 8666 shape code system (widely used on international projects alongside German DIN 488 supply) and the equivalent DIN 488 shape designations.

The Standard Columns of a Bar Bending Schedule

Bar Mark: The Identity Anchor

The bar mark (sometimes called bar reference) is the alphanumeric code that links every row in the BBS to a specific location on the structural reinforcement drawing. A bar marked “T3” on the schedule corresponds to a bar labelled “T3” on the drawing, shown in its structural position with cover dimensions and spacing indicated. Never place a bar in a location other than the one specified for its bar mark — bar marks are specific to structural positions, not interchangeable.

Shape Code: Defining the Bend Geometry

Shape codes are standardised two-digit numbers that define the geometry of the bent bar — the number of bends, the bend angles, and how the leg dimensions (A, B, C, etc.) relate to the finished shape. Under BS 8666 (widely used on UK and international projects):

• Shape 00 — Straight bar. Only dimension A (total length) applies.
• Shape 11 — L-shaped bar (one 90° bend). Dimensions A and B.
• Shape 21 — Z-bar or cranked bar (two bends). Dimensions A, B, C.
• Shape 32 — U-bar / starter bar (two 90° bends, open). Dimensions A, B, C.
• Shape 51 — Closed rectangular stirrup/link (four 90° bends + 135° hooks). Dimensions A, B — the most common stirrup form.
• Shape 67 — Helical bar (spiral reinforcement for circular columns/piles).

DIN 488-compliant fabrication in Germany uses equivalent shape designations referenced in German rebar detailing practice, which align with ISO 3766. If your project BBS uses BS 8666 codes and you are sourcing cut-and-bend from a German fabricator, confirm shape code equivalence in the order documentation.

Diameter and Weight Calculation

Once you know the diameter and cutting length of a bar, you can calculate its weight using the standard formula: weight (kg/m) = d² (mm) × 0.00617. This gives the theoretical weight per metre; multiply by cutting length in metres to get weight per bar, then by total number of bars for the total weight of that bar mark.

The total weight column in a BBS is indicative — actual delivery weights will reflect mill tolerances (DIN 488 permits ±4.5% on cross-section for individual bars) and will be documented on the delivery note and Mill Test Certificate. Use BBS weight totals for procurement planning and transport estimation; use MTC weights for formal payment quantities where contracts are priced by weight.

Reading the Dimension Columns: A Worked Example

Consider a BBS row with: Bar Mark B7 | Grade B500B | Dia 16 | Shape 51 | A=300, B=500 | No. Members 4 | Bars each 12 | Total 48 | Length each 1760 mm.

• Shape 51 = closed rectangular stirrup. Dimensions A and B are the internal dimensions of the link.
• A=300, B=500 — internal width 300 mm, internal height 500 mm.
• Cutting length 1760 mm — the straightened length before bending. This is the length that goes into the weight calculation and determines how many bars can be cut from a 6 m or 12 m stock length.
• 48 bars total × 1.760 m × 1.58 kg/m = approximately 133 kg for this bar mark alone.

This worked example illustrates why the BBS is also a procurement tool: totalling the weight column across all bar marks gives the approximate tonnage to order, broken down by diameter. Our cut-and-bend service page explains how we process BBS-based orders, and our products page covers straight bar supply for BBS items that are bent on site rather than in the fabrication yard.

Common BBS Reading Errors and How to Avoid Them

• Confusing cutting length with overall dimensions: The “length each” column is the cutting length (before bending), not the overall finished dimension. Ordering stock bar at the cutting length is correct; expecting the bent bar to measure that length in any direction is not.
• Ignoring the shape code: A bar marked with shape 21 and the same dimensions as a shape 11 bar will have a completely different geometry. Always check the shape code before fabrication.
• Wrong diameter: 12 mm and 16 mm bars have different weight per metre (0.888 vs 1.58 kg/m) and cross-section (113 vs 201 mm²). A BBS error on diameter that is not caught before pouring is a structural non-conformance.
• Not checking grade: If the BBS specifies B500B and straight B500A bar (coil-origin) is substituted, the ductility class requirement may not be met for the structural element — even though yield strength is identical.