Artificial Grass Calculator

How the artificial grass calculator works

Enter the lawn dimensions, the roll width, a wastage allowance, and a price per square metre. The calculator works out how many full-width strips are needed to cover the area, the length to order off the roll, the total grass area to buy including wastage, and an indicative material cost. Artificial grass is sold off a roll of fixed width, so the quantity to order is driven by how the rolls lay out across the area, not by the bare lawn area alone.

Rolls, strips, and how the quantity is worked out

Artificial grass comes on rolls of a set width — most commonly 2 m or 4 m — cut to whatever length is needed. To cover a lawn, full-width strips run along its length, side by side, until the width is covered. The number of strips is the lawn width divided by the roll width, rounded up: a 5 m-wide lawn off a 4 m roll needs two strips. Each strip runs the full lawn length, so the grass to order is the number of strips × roll width × length, plus the wastage allowance. Because the strips are full-width, the order area is usually larger than the lawn area — the surplus is trimmed off at the edges.

A worked example

Take a lawn 6 m long and 5 m wide, a 4 m roll, 10% wastage, at £18/m². The width needs ⌈5 ÷ 4⌉ = 2 strips. Each strip runs the 6 m length, so the base is 2 × 4 × 6 = 48 m². Adding 10% gives 52.8 m² to order, which is 13.2 m of length off the 4 m roll (2 × 6 × 1.10). At £18/m² the indicative material cost is 52.8 × £18 = £950.40. The bare lawn is 5 × 6 = 30 m²; the gap between that and the 52.8 m² ordered is the full-width surplus plus the wastage allowance.

Wastage and seams on artificial grass

For a plain rectangular lawn, 5–10% over the strip quantity covers trimming and squaring up. Shaped lawns, curved edges, or layouts with several cut-outs for trees, beds, or paths run higher — 15–20% is common. Where two strips meet, the join is made with jointing tape and adhesive, and an allowance lets the seam be cut clean. The wastage figure here is applied to both the order area and the linear length, so the cost reflects what is actually bought.

Pile direction and joins

Artificial grass has a pile that leans one way and reads differently by viewing angle, so every strip is laid with the pile running the same direction — usually toward the main viewpoint, such as the house or patio. That is why strips run along the area length in this calculation rather than being mixed in orientation: matching pile direction across each join keeps the finished lawn uniform. A seam where the pile of two strips opposes shows as a visible line.

Sub-base and what sits under the grass

The grass itself is the visible layer; underneath sits a prepared base. A typical build-up is a compacted sub-base of MOT Type 1 or granite dust, a laying course of sharp sand or grano dust screeded level, and sometimes a shockpad layer for play areas. The base governs drainage and how the surface wears, but it is a separate quantity from the grass — this calculator covers the grass roll only.

Which roll width to choose

Roll width drives waste. A lawn close to a roll-width multiple — for example a 4 m-wide lawn off a 4 m roll — wastes little, while an awkward width can leave a wide offcut. Where a lawn width falls just over a roll width, comparing a 2 m and a 4 m roll sometimes cuts the surplus. The roll-width input lets the layout be tested against the rolls a supplier actually stocks.

Reading the results

The headline figure is the grass area to order, including wastage — the quantity to give a supplier. The breakdown shows the bare lawn area for reference, the number of strips, the linear length to order off the roll (the figure a supplier cuts to), and the indicative cost. Because the cost is taken from the order area rather than the bare lawn, it matches what is actually paid.

What this tool does not do

It sizes the grass roll and its indicative cost. It does not size the sub-base, sand, shockpad, jointing tape, or adhesive, does not account for infill on sand-dressed systems, and does not confirm whether a particular build-up needs drainage or planning input. Those sit with the installer and, where relevant, the local authority.

Using this artificial grass calculator alongside other BuildMetricLab tools

The base under the grass is a separate take-off: the edging, decking, and fencing tools cover borders and the boundary, and the block-paving and compost tools cover adjacent ground works. Every BuildMetricLab tool runs entirely in your browser — no sign-up, no data sent anywhere, and the formula is shown on the page so the maths can be audited.