Artificial Grass Calculator

How Much Artificial Grass Do I Need?

The usual answer is the lawn area plus 5-15%. For a 6m × 4m lawn that is about 27 m². But grass is sold in fixed widths, either cut to length in whole metres or as fixed-size rolls, so what you buy depends on the product. On B&Q's 4m wide grass this lawn needs 9m of 4m wide, which is 36 m² bought for a 24 m² lawn.

So this calculator lays the lawn out. It cuts it into strips with the pile all running one way, adds a 50mm trim allowance at the outside edges and a 50mm overlap at each seam (both from Wickes' guide), packs the strips across the roll, and then works out the order the way each product is sold. The same lawn needs 17m of 2m wide or 7m of 5m wide. It cannot be laid from B&Q's 4m × 4m fixed rolls without a join across a strip.

Near-fit lawns. A 4m wide lawn needs 4.1m of grass across it with the trim, so on a 4m roll the Wickes rule needs a second strip and a seam: 9m of 4m wide. Laid tight to the two side edges, with no trim margin on those sides, it needs 7m of 4m wide and no seam. The calculator shows both whenever a lawn is within the trim allowance of the roll width. Keeping the trim is the default, because it is Wickes' method.

No percentage is added on top, because the trims and overlaps are already in the layout.

How the Layout Works

• Pile all one way. Wickes: "make sure that the pile all runs in the same direction". Strips run one way across the lawn, and you choose which way so the pile faces the house or the view.
• 50mm at every outside edge. Wickes: "a 50mm overlap on all outside edges and between any sections". Each strip is 50mm longer than the lawn at each end.
• 50mm overlap at each seam. It is trimmed off when the seam is cut, leaving a 1-2mm gap (Wickes).
• Fewest strips, best fit. The strips can be full roll width plus one narrower strip, or all the same width. The calculator tries both, and both ways round the lawn, and keeps the one that needs the least roll.
• Strips packed onto the roll. Rows across the roll are filled longest first, so a 2m strip and another 2m strip can share one length of a 4m roll.
• Bought as sold. Cut-to-length grass is ordered in whole metres, up to the product's longest length. A fixed roll is ordered as whole rolls, and a strip longer than the roll cannot come from it.
• Near-fit lawns. If the lawn is no wider than the roll but the trim makes it wider, you can keep the trim (with a seam) or lay one strip tight to the side edges. The strip ends keep their trim either way.
• Several lawns. Up to four rectangles, packed together.

What it does not do: it does not lay curves, count the sub-base or weed membrane, or edging, and it does not choose the pile direction for you. Enter a curved lawn as its bounding rectangle and use the extra allowance.

Products and How They Are Sold, With Sources

Every product in the dropdown has a supplier page that states its width and how it is sold, and no product page means no dropdown entry. The whole-metre lengths come from each page's size selector. Check your supplier before ordering.

Where the Rules Come From

The trim and overlap allowances, the pile direction and the sand rate are from Wickes' guide to installing artificial grass. The 2m and 4m widths and the extra length for trimming are from Jewson's guide. The 15cm pin spacing is from Tuda Grass' installation guide. Packing the strips onto the roll in rows, choosing between equal strips and full-width strips, and the option to lay a near-fit lawn tight to its side edges, are our own working.

Common Lawns: What to Order

Generated from the calculator above. Each lawn is one rectangle, with the strips running whichever way needs less grass and nothing added. Each cell keeps Wickes' 50mm trim. Where a lawn nearly fits the roll width, the no-seam option laid tight to the side edges follows as "tight". That happens in 5 of 6 lawns. The "area + 10%" column is the usual rule of thumb for comparison.

Use the calculator for your own lawn. The product changes both the area you buy and the number of seams.

Frequently Asked Questions

How much artificial grass do I need?

The usual sum is the lawn area plus 5-15%. For a 6m × 4m lawn that is about 27 m². But grass is sold by the roll, in fixed widths, so what you buy depends on the product. Some are cut to length in whole metres, and some come as fixed-size rolls. On B&Q's 4m wide grass, cut to length, this lawn needs 9m of 4m wide with Wickes' 50mm trim kept all round (36 m², 1 seam). Laid tight to the two side edges it needs 7m of 4m wide and no seam. On a 5m roll it needs 7m of 5m wide. The calculator lays out every strip and works out the order for each product as it is sold.

How is artificial grass sold?

It depends on the product. B&Q's 30mm grass listing sells 2m and 4m widths in whole-metre lengths from 1m to 20m. Grass Warehouse's Hestia 30mm comes in 4m and 5m widths, in whole metres from 1m to 25m. B&Q also sells a 30mm grass as a fixed 4m × 4m roll, which is bought as whole rolls. A fixed roll cannot supply a strip longer than the roll, so a 6m × 4m lawn cannot be laid from 4m × 4m rolls without a join across a strip, which the calculator does not lay. A 3m × 2m lawn takes 1 roll of 4m x 4m.

My lawn is almost exactly the roll width. Do I need a seam?

With Wickes' rule, yes. Wickes says to leave a 50mm overlap on all outside edges, so a 4m wide lawn needs 4.1m of grass across it, which is wider than a 4m roll. The other way is one strip laid tight to the two side edges, with no trim margin on those sides. The calculator shows both. For a 6m × 4m lawn on a 4m roll that is 9m of 4m wide with a seam, or 7m of 4m wide with no seam. For a 3m × 2m lawn on a 2m roll it is 5m of 2m wide with a seam, or 4m of 2m wide with no seam. Laying tight is our option, not Wickes' method: there is nothing spare to trim to the edge, so it only suits straight, square edges.

Which product and width is best?

The results rank every product for your lawn. Anything within 5% of the least area bought counts as a tie, and a tie goes to the fewest seams, because seams are the hardest part to get right. For a 6m × 4m lawn with the trim kept, the top pick is 5m wide, cut to length (Grass Warehouse) (7m of 5m wide, no seam). Where two products come out level on both, neither is called the top pick. Jewson says to consider the roll width when measuring to minimise joins.

Which way should the strips run?

All the pile must run the same way, so the strips run one way across the lawn. Wickes says to make sure the pile all runs in the same direction, and that fake grass usually looks best with the pile facing the house. Jewson says the same. The calculator's default tries both ways and uses the one that needs less grass, and you can force the strips along the length or the width to face the pile the way you want.

Why are the strips longer than the lawn?

Wickes says to leave a 50mm overlap on all outside edges and between any sections. So every strip is 50mm longer than the lawn at each end, the strips are 50mm wider than the lawn at each outside edge, and each seam takes a 50mm overlap. The overlap is trimmed off when you cut the seam, and Wickes says to leave a consistent 1-2mm gap between the sections. Jewson also says to allow for extra length, as you lose some when trimming and fitting.

How do I join the seams?

With joining tape and adhesive. Jewson says jointing tape and glue are all you need to fix different rolls together, and Tuda Grass says to secure the join with jointing tape and adhesive and let it cure fully. B&Q sells 300mm wide joining tape in 100m rolls. The results give the total seam length, which is the length of tape you need.

How many pins or nails do I need?

Tuda Grass says to fix the perimeter with galvanised nails spaced 15cm apart on a soil base. The calculator counts one every 150mm round the outside of each lawn. For a 6m × 4m lawn that is 134. It does not count pins along the seams, because we have no sourced spacing for them.

Do I need sand infill?

Wickes says spreading block paving sand over the finished grass is optional and adds stability, at a rate of about 5kg per m². For a 6m × 4m lawn that is 120kg. Check the manufacturer's advice for your grass, since some do not want infill.

What about the base underneath?

Wickes says a 75mm layer of aggregate such as MOT Type 1, with a 20-40mm layer of fine aggregate on top, and a weed membrane over the whole base. This calculator counts the grass only. Use our sub-base calculator for the aggregate.

What if a strip is longer than the product allows?

B&Q's cut-to-length grass goes up to 20m and Grass Warehouse's up to 25m. A longer strip needs a join across the lawn, which the calculator does not lay, so it warns you. Split the lawn into two, or run the strips the other way.

Does it work for curved or L-shaped lawns?

Enter each rectangle as its own lawn, and the strips from every lawn are packed onto the roll together. For a curved edge, enter the bounding rectangle, keep the trim, and raise the extra allowance, because the strips are drawn for the rectangle.