About this calculator
Estimates the take-off for a gabion (wire basket) retaining wall: basket count from a simple grid packing, stone fill volume and mass, and geotextile behind and beneath the wall.
Formula
baskets = ceil(wall length / basket length) × ceil(wall height / basket height) × ceil(wall depth / basket depth)
fill volume = baskets × (basket length × basket height × basket depth)
net stone (solid) volume = fill volume × (1 − void ratio%)
stone mass = fill volume × bulk density
geotextile area = wall length × (wall height + wall depth)
geotextile area incl. overlap = geotextile area × (1 + overlap% / 100)
geotextile rolls = ceil(geotextile area incl. overlap / roll area)
Fill volume is the total volume every basket must be packed with (the number you fill on site); net stone volume applies the void ratio to give the solid rock volume, useful if your supplier quotes solid m³ rather than fill volume. Stone mass uses bulk density directly (bulk density already accounts for the gaps between stones), so it does not need the void ratio applied a second time.
Worked example
Defaults: 10 m × 1 m × 0.5 m wall, 2 × 0.5 × 0.5 m baskets, 30% void ratio, 1700 kg/m³ bulk density, 10% geotextile overlap, 50 m² rolls.
baskets = ceil(10000/2000) × ceil(1000/500) × ceil(500/500) = 5 × 2 × 1 = 10
fill volume = 10 × (2 × 0.5 × 0.5) = 5 m³
net stone volume = 5 × 0.70 = 3.5 m³
stone mass = 5 × 1700 = 8500 kg
geotextile area = 10 × (1 + 0.5) = 15 m²; incl. overlap = 16.5 m² → 1 roll
FAQ
Why is the void ratio separate from bulk density? Bulk density (mass per fill volume) already includes the gaps between stones, so it alone gives the correct mass to order. The void ratio is only used to convert fill volume into a solid rock volume, which some quarries quote separately from bulk density.
Why doesn't the calculator cite a standard?
Basket size, void ratio, and bulk density all depend on the basket product and stone source —
no single standard fixes them, so meta.standards is left empty.
Assumptions and limits
Baskets are packed as a simple grid along each axis, rounded up on each — not a real coursing or bond pattern between adjoining baskets. Void ratio, bulk density, and geotextile overlap are all disclosed estimates you should adjust to match your own product and stone source.