How the artificial grass calculator works
Synthetic turf comes off a roll of fixed width and is sold by the linear metre or foot, so you pay for full widths even where your garden is narrower. The job is to decide which way the strips run and how many to cut. The calculator tries both directions: strips running along the length, laid side by side across the width, and the reverse. For each it rounds the number of strips up, adds a trimming allowance of 15 cm (6 in) to every strip, and keeps the layout that uses the least turf.
Turf = ⌈span across ÷ roll width⌉ × roll width × (strip length + trim)Every strip beyond the first creates a seam, glued onto joining tape laid underneath; tape is given with 10% extra for overlaps at ends. Infill sand is brushed into the pile to weigh the lawn down and keep fibres upright. It is calculated on the finished area at the rate you enter.
Worked example
A garden 8 m long and 5 m wide, with 4 m wide turf. Running strips along the 8 m length needs two strips (5 ÷ 4 rounded up), 2 × 4 × 8.15 = 65.2 m². Turning them to run across the 5 m width also needs two strips (8 ÷ 4 = 2), but only 2 × 4 × 5.15 = 41.2 m² of turf, so that layout wins: two 5.15 m cuts, one 5 m seam, 5.5 m of joining tape. At 5 kg/m² the 40 m² lawn takes 200 kg of kiln-dried sand, eight 25 kg bags, and the offcut waste is only 2.9%.
In the US, a 24 × 20 ft yard with 15 ft rolls needs two 20.5 ft strips (615 ft²) for 480 ft² of lawn, 22% waste. Ordering two 12 ft widths instead gives 2 × 12 × 20.5 = 492 ft²: always check the other roll width before buying.
Roll sizes and infill rates
| Item | Common sizes | Notes |
|---|---|---|
| Turf rolls, Europe | 2 m and 4 m wide, cut to length up to about 25 m | Some ranges also in 5 m |
| Turf rolls, North America | 12 ft and 15 ft wide, cut to length up to about 100 ft | Priced per ft² |
| Pile 20–30 mm (¾–1¼ in) | 4–6 kg/m² (0.8–1.2 lb/ft²) sand | Short, hard-wearing |
| Pile 35–40 mm (1⅜–1⅝ in) | 6–8 kg/m² (1.2–1.6 lb/ft²) sand | Denser, more natural look |
| Joining tape | 15–30 cm (6–12 in) wide rolls of 5–15 m | Use with two-part or moisture-cure adhesive |
| Sub-base | 75–100 mm (3–4 in) crushed stone | Plus 20–25 mm (¾–1 in) of grit or stone dust |
Mistakes that show in the finished lawn
- Mixed pile direction. All strips must lean the same way, ideally towards the house or main viewpoint, or each strip looks a different shade.
- Visible seams. Butt the edges without overlap and leave one row of tufts, about 1 cm, between factory edges; trim the selvedge off first.
- Using offcuts blindly. A 1 m infill strip cut from a 4 m roll saves money only if its pile runs the same direction as the rest.
- Skipping the sub-base. Laid straight on soil, turf ripples and puddles within a season.
- Fitting on a cold day. Turf contracts in cold weather; let it relax in the sun for a few hours before final cutting.
Frequently asked questions
What width does artificial grass come in?
In Europe rolls are usually 2 m or 4 m wide; in the US and Canada they are 12 ft or 15 ft wide. Length is cut to order, so you pay for the full width times the length you need.
How much artificial grass do I need for a 5 x 5 m garden?
With a 4 m roll you need two strips, for example a 4 m and a second 4 m cut trimmed to 1 m, about 2 × 4 × 5.15 = 41 m². A 4 m and a 2 m strip together (31 m²) waste much less.
How much sand do I need for artificial grass?
Most landscape turf takes 4–8 kg of kiln-dried silica sand per m², roughly 0.8–1.6 lb per ft². A 40 m² lawn at 5 kg/m² needs 200 kg, or eight 25 kg bags.
How do I hide the seams in artificial grass?
Cut the edge rows off both strips, lay them tight with the pile running the same way, and glue them onto joining tape with the adhesive recommended by the maker. Brush the fibres up once the glue has cured.
Do I need joining tape for every seam?
Yes. Plan about 10% more tape than the total seam length; a 5 m seam uses about 5.5 m of tape, and perimeter edges are fixed with pins or nails instead.
Last reviewed: 2026-09-27 · How we calculate