Dimensions. W and D are the overall rectangular concrete member width and depth; c is cover to the outside stirrup envelope from all four concrete faces; d is bar diameter. Full outside diagonals X=W−2c and Y=D−2c. Each equal side H=√[(X/2)²+(Y/2)²]. The image’s 450 × 200 mm diamond corresponds to a 500 × 250 mm member at 25 mm cover.

Adopted practical diamond length. L=4H+2T−[3(3d)+2(3d)]=4H+2T−15d. The reference supplies five 3d allowances. Retain the updated template’s T=max(8d,75 mm) straight extensions, rather than the older article’s 9d hooks. This is an estimating convention, not a verified exact IS diamond fabrication equation; do not add Table VIII allowances.

Ductile / seismic preset. The fixed preset adopts T = max(8d, 75 mm). The 15d deduction is a reference-derived practical BBS convention, not a complete developed bend-arc calculation or a cutting-length equation printed in IS 2502 or IS 13920. The straight-extension basis uses IS 13920:2016 with Amendment No. 1 (2017) and Amendment No. 2 (2020).

Straight hook extension. IS 2502:1963 clause 3.8 requires at least 8d straight extension beyond the end curve. The fixed seismic preset adopts max(8d, 75 mm), following the referenced IS 13920:2016 detail and Amendment No. 1 (2017). This is not the complete curved hook length. IS 2502 / IS 13920 — code book downloads

Scheduling & quantities. IS 2502:1963 clause 5.1.1 specifies the next greater whole 25 mm of the bending dimensions and allowances, not nearest-25 rounding. Scheduled length = ceil(calculated length ÷ 25) × 25; an exact multiple is unchanged. Table XI cutting tolerance is separate. Quantities and weights use this scheduled length. Wastage does not change the stirrup’s cutting length or count.

Display units. Lengths show mm, inches and feet, with the selected member unit first. Whole-unit display rounds fractions greater than .500 upward and exactly .500 downward. Feet use construction notation such as 5’2″ ft. Display rounding never changes the underlying geometry, cutting schedule or steel weight; calculation substitutions retain precision in mm.

Nominal mass. Standard diameters use IS 1786:2008 Table 1 masses: 6 mm = 0.222, 8 mm = 0.395, 10 mm = 0.617, 12 mm = 0.888, 16 mm = 1.58 kg/m. Other supported standard sizes use the same table. Nonstandard custom diameters use πd²/4 × 0.00785 kg/m, assuming steel density 7,850 kg/m³.

Scope. A centred rhombus link inside a rectangular or square concrete member, with closure at the top. Actual turns at left/right are 180°−2 atan(Y/X), with bottom turn 2 atan(Y/X). For equal diagonals the corner turns are 90°; the image’s universal 135° labels are not exact geometry. The adopted 15d allowance is held constant for practical reference estimates. This tool does not verify bend radii, longitudinal-bar engagement, hook fit, confinement, spacing or cross-ties. Check the approved drawing/BBS and a trial stirrup before batch cutting. Seismic diameter is at least 8 mm; some details require more.

IS code books used in civil engineering — PDF downloads