Artificial Grass Calculator — How Much Fake Grass Do I Need?

Our artificial grass calculator works out all the materials you need for a complete installation, including the grass itself, sub-base preparation, weed membrane, and fixings.

The formula

Grass area = Length × Width × Wastage factor
Sub-base (kg) = Area × 0.05m depth × 2,100 kg/m³ (compacted Type 1)
Sharp sand (kg) = Area × 0.015m depth × 1,600 kg/m³
Edging pins = Perimeter ÷ 0.2m spacing

Installation layers

• Sub-base: 50mm minimum compacted Type 1 MOT (≈2.1 tonnes per m³). Bought loose and compacts ~10–15%, so allow a 5–10% margin.
• Levelling layer: 15–25mm sharp sand or granite/limestone dust (≈1.6 tonnes per m³)
• Weed membrane: 100g/m² minimum non-woven, 150–200mm overlaps (calculator allows 10% over grass area)
• Artificial grass: Available in 2m and 4m wide rolls
• Edging pins: Galvanised U-pins, typically every 100–300mm around the perimeter (default 200mm — a trade convention, not a regulated value)

Sub-base depth, density and pin spacing are aggregate-supplier and installer conventions rather than figures set by a British Standard. The Type 1 density (2.0–2.2 t/m³, 2.1 t/m³ working estimate) follows UK aggregate-supplier guidance (Armstrongs Group; Soils & Stone, SHW Series 800 Clause 803). Joining tape is estimated for side-by-side strip seams only — add the extra seam length if your area is longer than the supplied roll and rolls must be butted end-to-end.