Tie wire quantity calculator

Instead of counting every crossing, this uses the reinforcement tonnage as a proxy — the method quantity surveyors use on tender: Wire (kg) = tonnes × rate × pattern.

The rate falls as bars get thicker, because a tonne of thin bar contains far more intersections than a tonne of thick bar: 8 mm ≈ 12, 10–16 mm ≈ 10, 20–25 mm ≈ 8, 28–32 mm ≈ 7 kg per tonne. Independent estimating tables put the typical figure in the 9–13 kg/tonne range, which brackets these bands.

Pattern factor is 1.0 for tying every intersection and 0.6 for a checkerboard/half pattern (not 0.5, because the perimeter and laps are still fully tied). A ±15% band is reported as an explicit uncertainty covering tie technique, spacing and offcuts.

3.2 t of 12 mm bar tied at every crossing → 3.2 × 10 × 1.0 = 32 kg (≈27–37 kg with the band); a half pattern ≈ 19 kg.

The rate assumes typical slab/wall spacing, so it is diameter-driven and does not track spacing explicitly — for very tight (<125 mm) or very wide (>300 mm) grids, cross-check with the intersection-count method (Slab reinforcement estimator). It excludes wire for splice cages, starters and column ties beyond normal slab/wall work.