What this calculator works out
Artificial grass comes off a roll of fixed width, so ordering the right amount is really two problems at once: how many full-width strips does the lawn need, and which way round should those strips run. This tool takes a lawn's length and width, tries both directions, strips running along the length and strips running along the width, and recommends whichever one wastes less roll and leaves fewer joins, then turns that into a strip count, a roll length to order, joining tape, and optional sub-base and weed membrane quantities.
It covers both major markets. UK rolls come in 2m or 4m widths, the sizes quoted by Grass Direct and Artificial Grass Direct; US rolls come in 12ft or 15ft widths, the sizes listed by Home Depot and Lowe's. Lawn length and width each carry their own metric or imperial toggle, so a garden measured in metres can still be matched against a US roll width, or the other way round, without converting anything by hand.
How the lay direction is worked out
Artificial grass has a pile, meaning the fibres are set leaning in one direction during manufacture, the same way a carpet or a velvet cushion has a nap. Every strip laid on a lawn has to face that pile the same way, or the join between strips catches the light differently and shows as a visible stripe once the sun is on it. That single rule is what makes lay direction matter: an offcut trimmed from the end of one strip usually cannot be turned round and reused facing the other way, even when there is plenty of material left in it.
Because of that, this calculator works out the order twice, once for each direction, rather than guessing. Laid "along the length", each strip is cut to the lawn's full length, and enough strips are laid side by side to span the width. Laid "along the width", each strip is cut to the lawn's full width instead, spanning the length. Both are genuine options; which one wins depends on how the lawn's proportions sit against the roll width.
Every strip has to be a full width of the roll, since a supplier cuts to length, not to width, so the strip count always rounds up. Joins are one fewer than the strip count, because strips laid side by side share a seam between each neighbouring pair, and joining tape has to run the entire length of every one of those seams, not just cover the middle of it.
The calculator compares the two directions on waste first: whichever orders less area for the same lawn wins. If both directions happen to waste exactly the same amount, the one with fewer joins wins instead, and if that also ties, laying along the length is used as the steady default, since it is the more commonly seen convention on a typical rectangular garden.
A worked example
Take a UK garden 6m long and 5m wide, buying a 4m-wide roll. Laid along the length, each strip is cut 6m long, and 2 strips (5m ÷ 4m, rounded up) are needed to span the width, ordering 2 × 4m × 6m = 48 m² against a real 30 m² lawn, 37.5% waste. Laid along the width instead, each strip is cut 5m long, and 2 strips (6m ÷ 4m, rounded up) span the length, ordering 2 × 4m × 5m = 40 m², 25.0% waste. Both directions need the same 2 strips and 1 join here, but laying along the width orders 8 m² less roll for the same lawn, so it is the one this calculator recommends. That 1 join needs 5m of joining tape, comfortably inside a single 10m tape roll. At a sample £14.99 per m², the 40 m² actually ordered comes to £599.60 for the grass, before underlay or labour.
The American equivalent: a 20ft by 15ft lawn buying a 15ft-wide roll. Laid along the length, each strip is cut 20ft long, and a single strip (15ft ÷ 15ft) spans the whole width exactly, ordering 300 sq ft against a 300 sq ft lawn, 0% waste and no joins at all. Laid along the width, each strip is cut 15ft long, and 2 strips (20ft ÷ 15ft, rounded up) are needed, ordering 450 sq ft, 33.3% waste. Here the difference is stark rather than marginal: matching the lawn's shorter side to the roll's width avoids a join altogether, which is the case worth watching for whenever one of the lawn's own dimensions is close to a stocked roll width.
UK 2m/4m rolls and US 12ft/15ft rolls
UK suppliers standardise on 2m and 4m widths for most garden-sized orders; both Grass Direct and Artificial Grass Direct list them as their core range, with a wider 5m roll available from both for larger lawns that would otherwise need an extra join. A narrower 2m roll suits a small courtyard, side passage or strip lawn well and is easier to manoeuvre and cut on site; a 4m roll covers a medium garden with fewer joins for the same area, at the cost of being heavier and needing more room to unroll and turn.
US retailers work in feet rather than metres, and 12ft and 15ft are the widths Home Depot and Lowe's both stock for cut-to-length residential turf. As the worked example above shows, matching a roll width closely to one of the lawn's own dimensions can remove a join entirely, so it is worth checking both available widths against the actual lawn shape before ordering, rather than defaulting to whichever is cheaper per square foot.
What goes underneath, and drainage
Artificial grass is only as good as the ground it is laid on, since there is no soil layer left to absorb small dips or soften a hard edge once the turf is down. The commonly published build-up is a compacted MOT Type 1 sub-base, 50mm deep for an ordinary domestic lawn or 75mm for a driveway, play area or anywhere seeing heavier use, topped with a thin blinding layer, typically 25mm, to give a smooth, even surface for the grass backing to sit on. Both NeoGrass's installation guide and whatsthebest.co.uk's sub-base guide give that same 50mm domestic / 75mm heavier-use split for the Type 1 layer, and both put the top layer at 25mm.
Where the two guides differ slightly is what that top layer should actually be. Sharp sand is the traditional answer and is what this calculator uses for its tonnage figure, but both sources now point installers toward granite or limestone dust instead, since sand shifts and forms shallow lumps underfoot as it dries and wets again through the seasons, while dust compacts and stays put. Either way, the depth and the resulting tonnage from this calculator's 25mm default apply the same; swap in your chosen material's own density if you know it differs from the 1.6 tonnes per m³ figure used here.
Drainage sits underneath this build-up rather than in a separate layer: a permeable MOT Type 1 base, laid with a slight fall away from the house, lets rainwater pass straight through the grass backing and the sub-base into the soil beneath, rather than pooling on the surface. A membrane laid directly on the compacted soil before the sub-base goes down, matching roughly the net lawn area with some overlap between sheets, also keeps weeds from pushing up through the joins later.
Questions people ask
Why can't leftover offcuts of artificial grass be turned round and reused?
The fibres are set leaning one way during manufacture, called the pile, the same idea as the nap on a carpet or velvet. A strip turned to face the other way catches the light differently to its neighbours, so the join shows as a visible line once the sun hits it, even though the material itself is identical.
Should I buy a 2m or 4m roll in the UK, or 12ft or 15ft in the US?
Whichever width sits closest to one of the lawn's own dimensions tends to waste the least and leave the fewest joins, which is exactly what this calculator's two-direction comparison checks for automatically. As a rule of thumb, a narrower roll suits a small or oddly shaped garden and is easier to handle on site; a wider roll suits a larger, regularly shaped lawn and cuts down on joins.
What goes underneath artificial grass?
A compacted MOT Type 1 sub-base, 50mm for a domestic lawn or 75mm for heavier use, topped with a thin 25mm blinding layer, either sharp sand or, increasingly, granite or limestone dust, to give an even surface for the grass to sit on.
Does artificial grass need drainage?
Yes. A permeable MOT Type 1 sub-base, laid with a slight fall away from the house, lets rainwater pass straight through the grass backing into the soil beneath rather than pooling on the surface, so drainage is built into the base layer rather than added separately.
How many joins will my lawn have, and does it matter?
Joins = strips − 1, so a lawn that fits one roll width exactly has none, and every extra strip adds one more. Fewer joins generally look neater and take less tape and adhesive, which is exactly why this calculator checks both lay directions rather than assuming one.
Roll widths, joining tape lengths and sub-base depths on this page are drawn from published supplier and installation guidance, checked against two sources each: Grass Direct and Artificial Grass Direct for UK roll widths, Home Depot and Lowe's for US roll widths, AVS Fencing and Artificial Grass GB for joining tape roll length, and NeoGrass and whatsthebest.co.uk for sub-base depths. Real gardens have corners, curves and slopes a simple rectangle can't capture fully; measure carefully and treat the figures here as a solid ordering estimate rather than a substitute for a site survey on an unusual lawn.