BS 8666 Shape Codes: The Complete Illustrated Guide (All Codes 00–99)
Every bar in a bar bending schedule needs a shape code — a two-digit number from BS 8666:2020 that tells the fabricator exactly how the bar is bent. This guide covers every standard shape code, with a diagram and the cutting-length formula for each, so you can look one up in seconds instead of digging through the standard itself.
What are shape codes?
A shape code is a standardised reference number (00–99) defined in BS 8666:2020, Specification for scheduling, dimensioning, bending and cutting of steel reinforcement for concrete. Each code corresponds to a specific bent-bar geometry — a straight bar, an L-bend, a closed stirrup, a spiral, and so on. Once a bar's shape code and dimensions (A, B, C…) are known, its exact cutting length can be calculated from the formula for that code, which is exactly what a bar bending schedule calculator does automatically. If you're new to reading a full schedule, our guide to reading a BBS covers how shape codes fit alongside bar marks, dimensions and weights.
How to read a shape code diagram
Each shape in BS 8666:2020 is drawn with its straight legs labelled A, B, C, D… in sequence around
the bar, following the direction the bar is bent. Dimensions shown in brackets, like (C), are
free dimensions — ones the detailer chooses, within limits, rather than ones fixed by the
design. The letter r is the bend radius and d is the bar diameter; both feed into the
length formula because bending steel around a radius shortens it slightly compared to the sum of the straight
legs. That shortening is called the bend deduction, and it's why the formula for almost every
bent shape below is "add the legs together, then subtract a bit for each bend."
The shape code directory
Jump straight to a code, or scroll through the full set. Codes 00–01 are straight bars, 11–15 have a single bend, 21–36 cover two- and three-bend shapes and cranks, 41–56 are hooked and closed links (including the standard stirrup, code 51), 63–77 are circular and helical shapes for columns and piles, and 98–99 cover anything non-standard.
- Shape code 00 — Straight bar
- Shape code 01 — Stock length bar
- Shape code 11 — Single bend (L-shape)
- Shape code 12 — Single bend, large radius
- Shape code 13 — Bend with 135° return
- Shape code 14 — Single bend, obtuse angle
- Shape code 15 — Single bend, acute angle
- Shape code 21 — Two bends, unequal legs
- Shape code 22 — U-bend + radius end
- Shape code 23 — Two bends, unequal legs (variant)
- Shape code 24 — Two 45° bends, unequal ends
- Shape code 25 — Two 45° bends, equal ends
- Shape code 26 — Cranked bar (staggered)
- Shape code 27 — Cranked bar, radiused
- Shape code 28 — Cranked bar, radiused (variant)
- Shape code 29 — Cranked bar, open ends
- Shape code 31 — Open box, radius down (22 inverted)
- Shape code 32 — Open box, radius rotated 180°
- Shape code 33 — Closed link, rounded ends
- Shape code 34 — Four-bend link variant
- Shape code 35 — Four-bend link variant
- Shape code 36 — Four-bend link variant
- Shape code 41 — Four-bend hook shape
- Shape code 44 — Four-bend hook shape (variant)
- Shape code 46 — Four-bend crank/hook
- Shape code 47 — Closed hook link
- Shape code 48 — Closed link, alternate hook
- Shape code 51 — Standard rectangular link (stirrup)
- Shape code 52 — Rectangular link, alternate corners
- Shape code 56 — Rectangular link with extended tail
- Shape code 63 — Circular link, three legs
- Shape code 64 — Circular link, multi-leg
- Shape code 67 — Circular ring / dowel
- Shape code 75 — Helical link, single turn
- Shape code 77 — Helical link, multiple turns
- Shape code 98 — Isometric / to-be-calculated shape
- Shape code 99 — Fully dimensioned custom shape
A plain straight bar cut to length A. The most common shape of all — used for main slab and wall bars, dowels, and laps.
Calculate shape 00 in the BS 8666 calculator →
A straight bar supplied in standard mill lengths (e.g. 6 m or 12 m). Dimension A is indicative for length calculations — delivery length is agreed with the supplier.
Calculate shape 01 in the BS 8666 calculator →
A bar with one 90° bend, forming an L. Extremely common for starter bars, kickers, and corner bars where a horizontal and vertical leg meet.
Calculate shape 11 in the BS 8666 calculator →
Similar to code 11 but bent around a larger radius (R), typically used where the bend needs to be gentler — for example a crank at a beam-column junction.
Calculate shape 12 in the BS 8666 calculator →
An L-shaped bar with an additional angled return at the end, often used for anchorage where a straight L isn't sufficient.
Calculate shape 13 in the BS 8666 calculator →
A bar bent through an obtuse angle at one end. The exact length depends on the true bend angle — see BS 8666:2020 Note 3.
Calculate shape 14 in the BS 8666 calculator →
Similar to code 14 but with an acute bend angle. Used where site geometry requires a sharper turn than 90°.
Calculate shape 15 in the BS 8666 calculator →
Often described as "one side of a box" — two 90° bends of different leg lengths. A workhorse shape for beam and pile cap cages.
Calculate shape 21 in the BS 8666 calculator →
Combines a U-bend at one end with a 90° radius at the other — effectively codes 12 and 13 joined. Common in retaining wall foundations.
Calculate shape 22 in the BS 8666 calculator →
A close relative of code 21 with a different dimensioning convention for the middle leg.
Calculate shape 23 in the BS 8666 calculator →
Turns the bar through 90° using two 45° bends rather than one 90° bend. Code 24 has two ends of different lengths.
Calculate shape 24 in the BS 8666 calculator →
The same idea as code 24, but the two end lengths are equal — useful where symmetry is needed either side of the bend.
Calculate shape 25 in the BS 8666 calculator →
Takes the bar through a stagger from one level to another using two open (obtuse) angles — the classic "cranked bar" used to step reinforcement between different cover levels.
Calculate shape 26 in the BS 8666 calculator →
A cranked bar variant with a radiused transition rather than a sharp stagger.
Calculate shape 27 in the BS 8666 calculator →
Closely related to code 27, with a different dimensioning arrangement for the offset.
Calculate shape 28 in the BS 8666 calculator →
Another cranked-bar variant used where the offset needs to sit closer to one end of the bar.
Calculate shape 29 in the BS 8666 calculator →
Geometrically the same as code 22, just oriented the opposite way — the direction matters for how the cage is assembled on site.
Calculate shape 31 in the BS 8666 calculator →
Takes the code 31 shape and rotates the radiused end 180°. Used where the open ends need to face a particular direction in the cage.
Calculate shape 32 in the BS 8666 calculator →
A rectangular link with two semi-circular ("paperclip") ends. A close cousin of the standard stirrup shapes below.
Calculate shape 33 in the BS 8666 calculator →
One of several four-bend shapes used for links and cranked cage members where geometry needs to change direction twice.
Calculate shape 34 in the BS 8666 calculator →
A close relative of code 34 with a different dimensioning split between the legs.
Calculate shape 35 in the BS 8666 calculator →
Another four-bend cage/crank shape, with the length found by adding the four legs and subtracting one bend deduction.
Calculate shape 36 in the BS 8666 calculator →
A bar with four bends forming a hooked profile, often used at construction joints or for anchorage into an adjoining pour.
Calculate shape 41 in the BS 8666 calculator →
Closely related to code 41 with a different arrangement of the end hooks.
Calculate shape 44 in the BS 8666 calculator →
A four-bend shape combining a crank with a hooked end. Its length equation is one of the ones BS 8666:2020 flags as approximate for steep bend angles.
Calculate shape 46 in the BS 8666 calculator →
A closed link with hooked ends (q is the hook diameter from BS 8666:2020 Table 2) — used where extra anchorage is needed beyond a standard stirrup.
Calculate shape 47 in the BS 8666 calculator →
A variant of code 47 with a simpler end-hook detail.
Calculate shape 48 in the BS 8666 calculator →
The classic closed stirrup/link shape used in beams and columns to resist shear and hold main bars in position — probably the single most-searched shape code.
Calculate shape 51 in the BS 8666 calculator →
A rectangular link very similar to code 51 with a different corner/leg dimensioning convention.
Calculate shape 52 in the BS 8666 calculator →
A link shape with an extended leg or tail beyond the standard rectangle — useful where the link needs to project further into an adjoining element.
Calculate shape 56 in the BS 8666 calculator →
A link shape built around a circular or near-circular profile with three straight legs — used for circular columns and piles.
Calculate shape 63 in the BS 8666 calculator →
A more elaborate circular link variant with additional legs, also aimed at circular column and pile cage reinforcement.
Calculate shape 64 in the BS 8666 calculator →
A simple circular ring or dowel bar shape, where A defines the ring diameter or straight dowel length depending on application.
Calculate shape 67 in the BS 8666 calculator →
A helical (spiral) link used for circular columns and piles — the formula is essentially the circumference of one turn, plus a small overlap allowance.
Calculate shape 75 in the BS 8666 calculator →
The multi-turn version of code 75, where C is the number of turns in the spiral. Common in piling cages where a continuous helical link runs the full length.
Calculate shape 77 in the BS 8666 calculator →
Used for shapes that need an isometric sketch to convey (e.g. 3D offsets, or bars scheduled to a coupler) — the length is calculated case by case rather than from a standard formula.
Calculate shape 98 in the BS 8666 calculator →
When a bar doesn't match any standard shape — or when bend angles approach 90° and the standard formulas become unreliable — it's drawn out in full and given shape code 99.
Calculate shape 99 in the BS 8666 calculator →Shape codes vs. the older BS 4466
BS 8666 superseded the older BS 4466:1989 standard, and BS 8666:2020 itself is a light revision of BS 8666:2005 — it added two new shape codes and amended the formulas or dimensioning for around twenty others, mainly around cranked bars and obtuse-angle bends. If you're working from an older drawing that references BS 4466 shape codes, the numbering doesn't map one-to-one onto BS 8666, so it's worth having the drawing re-checked against the current standard rather than assuming the codes are interchangeable.
Common mistakes when selecting a shape code
- Confusing similar-looking codes. Codes like 21/23, 24/25, and 31/32 look almost identical on a small sketch but differ in leg lengths or orientation — get the orientation wrong and the cage won't fit together on site.
- Forgetting the bend deduction. Adding up the straight legs without subtracting the radius/diameter term for each bend will over-state the cutting length, wasting steel across a whole schedule.
- Using a standard code for a non-standard angle. BS 8666:2020 flags several formulas (codes 14, 15, 24–29, 34–36, 46, 56) as approximate once the bend angle passes about 45°. Where a bend approaches 90° on one of these shapes, it's safer to schedule it as shape code 99 with a fully dimensioned sketch.
- Missing the minimum radius and end projection. Every shape code is subject to the minimum scheduling radius (r) and minimum end projection (P) in BS 8666:2020 Table 2 for that bar size — a dimension smaller than the minimum simply can't be bent.
Skip the manual lookup
Pick a shape code, enter the dimensions, and let the calculator apply the correct BS 8666:2020 formula and bend deduction automatically — then export straight to PDF or Excel.
Open the BS 8666 calculator →Frequently asked questions
What is shape code 21 used for?
Shape code 21 is a two-bend bar often described as one side of a box — two 90° bends of different leg lengths. It's a workhorse shape for beam cages, pile caps and similar reinforcement assemblies.
How many shape codes are there in BS 8666:2020?
BS 8666:2020 defines around 40 standard numbered shapes (00 to 77), plus code 98 for shapes needing an isometric sketch and code 99 for any fully custom shape that doesn't match a standard code.
What's the difference between BS 8666 and IS 2502 shape codes?
BS 8666:2020 is the British Standard used in the UK, while IS 2502 is the equivalent Indian Standard for bar bending schedules. The two use different shape code numbering systems, so a shape code from one standard does not carry over directly to the other — see our IS 2502 calculator if you're working to the Indian standard.
Where can I find a free shape code chart?
This page lists every standard BS 8666:2020 shape code with a diagram and formula. For the official reference, BS 8666:2020 itself (available for purchase from BSI) is the authoritative source.
Working to the Indian standard instead?
IS 2502 uses its own shape code numbering. Read the companion guide, then build your schedule in the free IS 2502 calculator.
Open the IS 2502 calculator →Not a substitute for a checked, engineer-approved bending schedule. Always verify dimensions, radii and end projections against BS 8666:2020 for the actual bar size in use.