AS/NZS 4671 Reinforcement

Purpose This calculator gives basic development lengths and lapped-splice lengths for straight deformed reinforcing bars in tension and compression in accordance with AS 3600:2018 (incorporating Amendments 1 and 2), Clauses 13.1.2.2, 13.1.5.2, 13.2.2 and 13.2.4. Assumptions Only the basic development length is calculated (Clause 13.1.2.2). No allowance is made for transverse reinforcement or transverse pressure (Clause 13.1.2.3). Reinforcement is deformed D500N bar complying with AS/NZS 4671; f_sy = 500 MPa. Wide elements or members (flanges, band beams, slabs, walls, blade columns): c_d = min(a/2, c) per Figure 13.1.2.2 (ii)(a) and Figure 13.2.2, where a is the clear distance between adjacent bars (development) or between adjacent lapped pairs (laps). Splices are contact splices with the lapped bars side by side in the plane of the element, so a = s − 2d_b for laps and a = s − d_b for development. k₇ = 1.25 (Clause 13.2.2). Tabulated lengths are rounded up to the nearest 10 mm. Cover used in the calculation is not taken as less than the bar diameter, and the bar spacing is not taken as less than 75 mm with a clear spacing of at least 30 mm; where an input is below these limits the adjusted value is reported and the tabulated length is based on it. Exclusions Narrow elements (beam webs and columns, Clause 13.2.2 second paragraph), hooked or cogged ends (Clause 13.1.2.6), plain bars, epoxy-coated bars, lightweight concrete, slip-formed elements, mesh, bundled bars, and the refined provisions of Clauses 13.1.2.3 and 13.1.5.3. Revision v2 (October 2026): all tables regenerated from AS 3600:2018 and independently verified across the full input range. v5 (October 2026): calculation working values (a, c_d, k₃) shown below the results, and input tooltips added; no change to any tabulated value.