How much artificial grass do I need?

Nearly everyone starts by working out the area of their lawn. It is the obvious thing to do, and on its own it will not tell you what to order. Artificial grass comes off a roll in fixed widths, and the width you pick decides more about your final bill than the size of your garden does. This guide walks through the measuring, the roll-width arithmetic, and three worked examples, so you can order once and order right.

The short answer

Measure the longest and widest points of the area, add 100mm to each, then choose the roll width that covers the shorter measurement with the least waste. Multiply that roll width by the longer measurement and you have the number of square metres to order. If the area is wider than the widest roll, plan a join. Our room calculator does the arithmetic for you, but it helps to understand why it gives the answer it does.

Step 1: measure the widest and longest points

Take the widest point of the area and the longest point, and treat the space as a rectangle even if it is nothing like one. Curves, borders and awkward corners are cut to shape after the grass is down, but the grass has to arrive as a rectangle big enough to cover everything inside those two measurements.

Measure in metres to two decimal places. Then add roughly 100mm to each measurement. That extra gives you something to trim against at the edges, which matters more than it sounds: a lawn cut exactly to size leaves no room for error, and the edges are where a lawn looks amateur or professional.

If the area has a bay or an L-shape, measure the overall rectangle first, then decide whether the offcut from the corner is big enough to fill another part of the garden. Often it is, and a path or side return can come out of the waste.

Step 2: understand roll widths

Every range we sell comes in 2m and 4m widths. Most also come in 5m, and several come in 1m and 3m. This is the table to keep in front of you.

Range	Pile	Widths available	Price per m²
Rocco	18mm	2m, 4m	£7.49
Talya	30mm	2m, 4m, 5m	£8.00
Dan	38mm	2m, 3m, 4m, 5m	£8.99
Bul	35mm	2m, 4m, 5m	£9.00
Rum	40mm	1m, 2m, 3m, 4m, 5m	£10.00
Jers	30mm	1m, 2m, 3m, 4m, 5m	£11.00
Val	38mm	2m, 4m, 5m	£11.00
Lux	30mm	1m, 2m, 3m, 4m, 5m	£12.50
Cali	40mm	2m, 3m, 4m, 5m	£13.50
Ens	38mm	2m, 4m, 5m	£13.50
Aris	40mm	2m, 3m, 4m, 5m	£15.00
Orf	45mm	2m, 4m, 5m	£17.00
Onto	40mm	2m, 4m, 5m	£18.00
Dluxe	40mm	2m, 4m, 5m	£19.00

You cannot buy 3.4m of width. You buy a 4m roll and trim 600mm off, or you buy a 2m roll and a 2m roll and join them. Which of those is cheaper depends on the length, and that is the whole game.

Step 3: pick the width that wastes least

Take the shorter of your two measurements and find the smallest roll width that is equal to or bigger than it. That roll runs the length of the longer measurement. The number of square metres you pay for is the roll width multiplied by the length, not the area of the lawn.

Two rules of thumb:

• If the shorter measurement is just over a roll width, say 4.1m, look hard at whether you can lose 100mm with a slightly wider border or a row of slabs. Dropping from a 5m roll to a 4m roll on a 10m lawn saves 10m² of grass.
• If the shorter measurement is just under a roll width, say 3.9m, you are in luck. A 4m roll leaves you 100mm to trim and almost nothing to bin.

Three worked examples

Example 1: a 4m by 6m family lawn

Widest point 4.0m, longest point 6.0m. Add 100mm each way: 4.1m by 6.1m. The shorter side is 4.1m, so a 4m roll is 100mm short. The options are a 5m roll at 6.1m long, which is 30.5m², or two 2m rolls joined down the middle at 6.1m each, which is 24.4m² plus a join. On Dan at £8.99 that is £274 versus £219 plus tape and adhesive, so the join saves around £45. On a lawn this size most people take the join because it runs under the middle of the garden where nobody looks.

The better answer is usually to make the lawn 3.9m wide. Widen the border by 100mm on one side, order a 4m roll at 6.1m, pay for 24.4m² with no join, and the border looks intentional.

Example 2: a 2m by 10m side return or path

Widest point 1.9m, longest 10m. Add 100mm: 2.0m by 10.1m. A 2m roll fits exactly, so you order 2m by 10.1m, which is 20.2m². On Rocco at £7.49 that is £151. A 1m roll would need a join down the middle of a narrow strip, which is the worst place for a join, so the 2m roll wins even though it is the same area.

If the same strip were 2.2m wide, you would be into a 3m or 4m roll and paying for 30 to 40m² to cover 22. That is when it is worth asking whether the strip can be 2m.

Example 3: a 7m by 9m lawn wider than any roll

Widest point 7.0m, longest 9.0m. Add 100mm: 7.1m by 9.1m. No roll is 7.1m wide, so a join is unavoidable. Two 4m rolls at 9.1m each give 8m of width for 72.8m², with 900mm of waste. A 5m roll plus a 2m roll at 9.1m each give exactly 7m, which is 100mm short, so that combination needs the lawn trimmed to 6.9m or the border widened. A 5m roll and a 3m roll at 9.1m give 8m for the same 72.8m² but from a range that offers 3m.

On a lawn this size the choice is rarely about the arithmetic. It is about where the join falls. Two 4m rolls put the join dead centre. A 5m plus 2m puts it 2m from one edge, which can tuck under a path or a border and disappear. Plan that before ordering, not on the day.

Joins are normal

Where the area is wider than the widest roll, you need two pieces and a join. Done properly with joining tape and adhesive, with the pile running the same way on both pieces, a join is invisible once the pile is brushed up. Three things make a join look bad: two pieces with the pile running in opposite directions, pieces from different batches, and a join placed where the light rakes across it in the evening. Order both pieces at once, from one batch, and place the join where you will not stand and stare at it.

Pile direction

Every roll has a pile that leans slightly one way. Lay it leaning towards the house, or towards wherever you normally view the lawn from, and the colour reads richer. Lay it away from you and the lawn looks paler and flatter. This affects how much you order in one specific case: if you are joining pieces, they must all lean the same way, so you cannot rotate an offcut 90 degrees to fill a gap. Keep that in mind before deciding the offcut from example 1 will cover the side return in example 2.

What else to order

For a lawn onto soil, the installation guide lists the sub-base and depths. In materials terms, for each 20m² you will typically need: weed membrane to cover the area with 100mm overlaps, roughly 1 tonne of MOT Type 1 for a 40 to 50mm sub-base, two to three bags of sharp sand for the blinding layer, a pack of galvanised U-pegs for the perimeter at 200 to 300mm centres, and joining tape with a tub of adhesive per join. On decking or slabs, swap the sub-base for shockpad underlay, which softens the surface and stops board lines showing through.

Order samples before you order a lawn

Grass looks different in your own garden than it does on a screen. North-facing gardens flatten the colour; strong sun lifts it. Pile height reads shorter outdoors than it does in a photograph. You can order up to five free samples and lay them on the ground where the lawn is going, on a normal day, before committing to a roll. It is the cheapest part of the whole job and it prevents the expensive mistake.

A quick checklist

• Measure the widest and longest points, not the area
• Add about 100mm each way for trimming
• Find the smallest roll width that covers the shorter measurement
• Square metres to order = roll width × the longer measurement
• If a join is needed, plan where it falls and order both pieces from one batch
• Keep the pile leaning towards where you view the lawn from
• Order samples and look at them outdoors

Stuck with an awkward shape? Call us on 0161 399 1792 with your two measurements and we will tell you what to order. Standard delivery is 2 to 4 working days across mainland UK, with next day available if you are in a hurry.