How this calculator works
Artificial grass comes on rolls of a fixed width, usually 2 m or 4 m, and you order a length. The grass is laid in strips from edge to edge, so the length to buy is the number of strips times the length of a strip, plus an allowance for trimming. The calculator tries laying the strips along the length and along the width of the lawn, and chooses the one that wastes less. The base is MOT Type 1 stone (about 2.2 tonnes per cubic metre compacted) with a layer of sharp sand on top, and a weed membrane goes under it.
Worked example: a lawn 5 m long and 4 m wide (20.0 m²) fits one strip of a 4 m roll: 5.3 m of roll with 5% extra, which is 21 m² of grass, with no joins. The base is 2.31 tonnes of MOT Type 1 (50 mm) and 0.84 tonnes of sharp sand (25 mm), with 22 m² of weed membrane and about 72 pins around the edge. A 2 m roll needs 10.5 m of roll and 1 join. A lawn 6 × 4.5 m is wider than the roll, so it needs two strips and a join: 9.5 m of roll (38 m² of grass). A 10 × 6 m lawn needs 18.9 m of roll, a 75 mm base takes 3.47 tonnes of MOT Type 1, and with no sand layer the sand is 0 tonnes.
Grass and base for common lawn sizes (4 m roll, 5% extra, 50 mm sub-base, 25 mm sand)
Roll length to order, and the tonnes of MOT Type 1 and sharp sand.
| Lawn | Area | Roll length | Grass to buy | MOT Type 1 | Sharp sand |
|---|---|---|---|---|---|
| 4 × 3 m | 12 m² | 3.2 m | 13 m² | 1.4 t | 0.5 t |
| 5 × 4 m | 20 m² | 5.3 m | 21 m² | 2.3 t | 0.8 t |
| 6 × 4.5 m | 27 m² | 9.5 m | 38 m² | 3.1 t | 1.1 t |
| 8 × 5 m | 40 m² | 10.5 m | 42 m² | 4.6 t | 1.7 t |
| 10 × 6 m | 60 m² | 18.9 m | 76 m² | 6.9 t | 2.5 t |
| 12 × 8 m | 96 m² | 25.2 m | 101 m² | 11.1 t | 4.0 t |
Tips before you buy
- Choose the roll width that covers the lawn in one strip if you can: joins are the part of an artificial lawn that show.
- Compact the sub-base in layers with a plate compactor, and rake it level with a slight fall for drainage, then add the sand and compact again.
- Lay the weed membrane over the sub-base, then the sand, and leave the grass to relax in the sun before you cut and fix it.
- Lay all strips with the pile leaning the same way, and keep the cut edges tight when you join them.
- Brush the pile up after you lay it, and add a kiln-dried sand infill if the manufacturer says so.
Tools & materials for this project
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Frequently asked questions
How much artificial grass do I need?
The area of the lawn plus a trim allowance, ordered as a length of a 2 m or 4 m wide roll. A 5 × 4 m lawn needs 5.3 m of 4 m roll (21 m²), and a 6 × 4.5 m lawn 9.5 m.
How much MOT Type 1 do I need for artificial grass?
For a 50 mm sub-base, about 0.12 tonnes per m², so 2.31 tonnes for 20 m². Add depth for soft ground: a 75 mm sub-base is 3.47 tonnes.
Do I need sharp sand under artificial grass?
A 25 mm layer of sharp sand over the sub-base gives a smooth, level surface: 0.84 tonnes for this lawn. Some installers use grit sand or fine stone dust.
How do I avoid joins in artificial grass?
Choose a roll that is as wide as the lawn, or lay the strips along the direction that needs fewer. A 4 m roll covers a lawn up to 4 m wide in one strip.
How many pins do I need?
About one every 25 cm around the edge: 72 for this lawn, plus extra along the joins and any curves.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.