How the artificial grass calculator works
Artificial grass comes on rolls of a fixed width (usually 2m, 4m or 5m) cut to any length. The calculator tries both directions: strips running along the length, and strips running across the width. It picks the layout that needs the least grass (and, if equal, the fewest joins), adding 10cm to each strip for trimming.
Sub-base for laying on soil
| Layer | Depth | Notes |
|---|---|---|
| Weed membrane | — | On the dug-out, levelled soil |
| MOT Type 1 | 50mm | Compacted with a plate compactor |
| Granite dust / sharp sand | 20–25mm | Screeded smooth and compacted |
| Weed membrane | — | Optional second layer under the grass |
| Artificial grass | — | Pinned at edges, seams taped and glued |
Laying tips
- Fit a firm edging (timber, composite or steel) so you have something to pin or glue the edges to.
- Unroll the grass and let it settle in the sun for an hour or two before cutting to remove creases.
- Line up seams so the pile runs the same direction, with the backing edges touching but not overlapping.
- Brush in kiln-dried sand in thin layers, then brush against the pile to lift it.
Worked example: a 6m × 4.5m lawn
The lawn is 27m². With 4m-wide rolls, running strips along the 6m length would need two strips 6.1m long (48.8m²). Running them across is better: two strips 4.6m long, so 36.8m² of grass with a single 4.5m join. That's still 27% waste, because 4.5m is just too wide for one 4m roll.
Switch to a 5m-wide roll and the whole lawn fits in one piece 6.1m long: 30.5m², no joins, and much less waste. Always compare roll widths before you order. The cheapest price per m² isn't always the cheapest lawn.
On soil, this lawn also needs about 3 tonnes of MOT Type 1 (4 bulk bags), 1.3 tonnes of granite dust (2 bulk bags), about 59m² of membrane for two layers, roughly 80 U-pins, and 6 bags of kiln-dried sand if the product uses infill.
Choosing artificial grass
- Pile height: 30–40mm looks natural for most gardens. Longer piles look lush but flatten more where people walk.
- Density: a higher stitch rate and more fibres per m² feel softer and recover better from foot traffic.
- Backing and drainage: check for a perforated, well-drained backing, especially if you have pets.
- Reflected sunlight: some energy-efficient windows can focus sunlight hard enough to damage synthetic fibres. If your lawn is overlooked by a south-facing window, ask the supplier about heat-resistant products.
Looking after it
Brush against the pile every few weeks to keep it upright, and clear leaves with a leaf blower or plastic rake. Rinse pet areas regularly. Weeds can root in debris on top, so pull them out while they're small. A well-laid lawn should drain like a gravel path, so puddles usually mean the sub-base wasn't compacted properly.
Common mistakes
- Laying straight on soil. Without a compacted sub-base the surface goes lumpy and holds water.
- Visible seams. Mismatched pile directions or gaps between strips show up badly. Join carefully on tape and adhesive.
- No edge restraint. The edges lift and curl without a firm border to fix to.
Weighing it up against real grass? The turf calculator prices the same area in turf rolls. For the base on its own, use the MOT Type 1 calculator, and the excavation calculator for the dig.