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Artificial grass calculator

Work out how much artificial grass to buy for your lawn. It tries 2 m and 4 m wide rolls, both ways round, and shows the length to order, the spare grass and the number of joins. It also works out the sub-base, sand and infill.

Man unrolling artificial grass over a prepared sub-base beside a brick house

MOT Type 1 and a sharp sand levelling layer.

Your result

Grass to buy

24 m²

4 m wide × 6 m long, strips along the length, for 21 m² of lawn.

2 m wide roll: length to buy
12 mstrips along the length; 24 m² bought for 21 m² needed; 1 join
4 m wide roll: length to buy
6 mstrips along the length; 24 m² bought for 21 m² needed; 0 joins
Spare grass from the best layout
3 m²offcuts, useful for patching
Joining tape
0 mno joins needed
MOT Type 1 sub-base
3.64 tonnes75 mm compacted; 5 bulk bags of 850 kg
Sharp sand or granite dust
0.89 tonnes25 mm levelling layer; 2 bulk bags of 850 kg. Granite dust weighs about the same.
  • Check the pile direction. It should lean towards where you will look at the lawn from, and all strips must lie the same way.
  • Suppliers cut rolls to length in set steps, so ask what your supplier rounds to, and leave a little to trim at the edges.

Add this to your project shopping list, then print it or take it to the merchant.

Open shopping list

How to use the artificial grass calculator

  1. Enter the Lawn length and Lawn width. Each box has its own unit, so you can use metres or feet.
  2. Leave Work out the sub-base switched on to get the MOT Type 1 and the sharp sand or granite dust layer.
  3. Switch on Add sand infill if your grass needs it. Skip it if you have pets that use the lawn.
  4. Read the Grass to buy result. It shows the roll width, the length to order and which way the strips run.
  5. Compare the 2 m and 4 m results to see the trade-off between spare grass and joins.
  6. Tap Add to shopping list to keep the result or Share link to send it to your supplier.

Why use this calculator

It does the joins versus waste trade-off for you. A narrower roll can use less grass but leaves more joins, which show in a lawn. The calculator picks the layout with the fewest joins unless that means buying more than 20% of the lawn area in extra grass.

It tries every layout. It works out 2 m and 4 m rolls, with the strips along the length and along the width, and shows you the numbers for each.

It adds the ground work. You get the MOT Type 1 sub-base, the sharp sand levelling layer and the infill in the same result.

It shows its working. Under How we worked it out you can see every layout it tried.

How we worked it out

Your numbers, step by step. This updates as you change the calculator.

  1. Lawn area = 6 m × 3.5 m = 21 m²
  2. 2 m roll, strips along the length: 2 strips, roll length 12 m, 24 m² bought (3 m² spare), 1 join
  3. 2 m roll, strips along the width: 3 strips, roll length 10.5 m, 21 m² bought (0 m² spare), 2 joins
  4. 4 m roll, strips along the length: 1 strip, roll length 6 m, 24 m² bought (3 m² spare), 0 joins
  5. 4 m roll, strips along the width: 2 strips, roll length 7 m, 28 m² bought (7 m² spare), 1 join
  6. Best layout (fewest joins, unless that wastes more than 20% extra grass): 4 m wide roll, 6 m long, strips along the length.
  7. MOT Type 1 = 21 m² × 75 mm × about 2.1 t/m³ × 1.1 allowance = 3.64 tonnes (5 bulk bags)
  8. Sharp sand or granite dust = 21 m² × 25 mm × about 1.7 t/m³ = 0.89 tonnes (2 bulk bags)

The formula

Grass comes on rolls of a fixed width and is cut to length. Strips are laid side by side, so the number of strips is the width you need to cover divided by the roll width, rounded up.

Strips = distance across ÷ roll width, rounded up Roll length = strips × length of each strip Joins = strips − 1

For a 6 m by 3.5 m lawn (21 m²), the calculator tries four layouts:

  • 2 m roll, strips along the 6 m length: 2 strips, 12 m of roll, 24 m² bought, 1 join.
  • 2 m roll, strips along the 3.5 m width: 3 strips, 10.5 m of roll, 21 m² bought, 2 joins.
  • 4 m roll, strips along the 6 m length: 1 strip, 6 m of roll, 24 m² bought, no joins.
  • 4 m roll, strips along the 3.5 m width: 2 strips, 7 m of roll, 28 m² bought, 1 join.

Joins show in a lawn, so the best layout is the one with the fewest joins, unless that means buying more than 20% of the lawn area in extra grass. Here that is the 4 m roll, 6 m long. Joining tape is the length of each join added up.

For the ground work:

  • MOT Type 1 = area × 0.075 m × about 2.1 tonnes per m³ × 1.10. For 21 m²: 3.64 tonnes, or 5 bulk bags of 850 kg.
  • Sharp sand or granite dust = area × 0.025 m × about 1.7 tonnes per m³. For 21 m²: 0.89 tonnes, or 2 bulk bags.
  • Sand infill = area × 5 kg. For 21 m²: 105 kg.

What we assume

  • Rolls are 2 m or 4 m wide and up to 25 m long. Some sellers also offer 5 m. We have not confirmed these widths with a manufacturer datasheet, so check your supplier’s range.
  • The sub-base is 75 mm of MOT Type 1, as Wickes suggests for clay or poor drainage. Other guides give different depths, so check the ground on your site and ask your installer.
  • The levelling layer is 25 mm of sharp sand. Wickes gives 20 to 40 mm, and other guides differ, so 25 mm is a middle-of-the-road choice. Granite dust is about the same weight.
  • Sand infill is about 5 kg per m², from Wickes, which also says sand is not advisable for pet owners. Not every grass needs infill, and pets change the answer.
  • MOT Type 1 is about 2.1 tonnes per m³ once compacted, with 10% added for compaction.

Tips

  • Look at the pile direction. The pile should lean towards where you will look at the lawn from, and all strips must lie the same way.
  • Suppliers cut rolls to length in set steps. Ask what your supplier rounds to, and leave a little to trim at the edges.
  • Ask whether your grass needs infill. The infill type depends on the grass and on whether pets use the lawn, so ask the maker, and do not use sand infill if you have pets.
  • Keep the offcuts. The spare grass from the best layout is useful for patching a worn spot later.
  • Work out the area of an awkward lawn first with the square metre calculator, then use the nearest rectangle here and add a little for the shape.
  • The base is the same job as a path or patio. The gravel calculator has MOT Type 1 if you want to check the stone on its own.

FAQs

How much artificial grass do I need for my garden?
The lawn area in m², plus the spare you get from rolls cut in strips. A 6 m by 3.5 m lawn is 21 m², and the best layout is a 4 m wide roll cut 6 m long, which is 24 m² with no joins.
What roll width does artificial grass come in, and how much will I waste?
Mostly 2 m and 4 m wide, with some sellers offering 5 m. Rolls are cut to length, up to about 25 m. For the 6 m by 3.5 m lawn, a 2 m roll cut 12 m long is also 24 m², but it leaves 1 join.
How many joins will I have?
Strips minus 1. A 4 m roll covers a 3.5 m wide lawn in one strip, so no joins. Laying 2 m strips the other way needs 3 strips of 3.5 m, which is 21 m² of grass but 2 joins.
How much sharp sand or granite dust do I need under artificial grass?
About 42 kg per m² for a 25 mm layer, which is 0.9 tonnes for 21 m². Granite dust weighs about the same, so the sums are the same for either.
How deep should the MOT Type 1 sub-base be for artificial grass?
75 mm, which is 3.6 tonnes of MOT Type 1 for a 21 m² lawn including the 10% compaction allowance. Wickes suggests starting with a 75 mm layer where there is clay or poor drainage. Follow the grass maker's instructions, because the depth depends on your soil.
How much sand infill do I need per m²?
About 5 kg per m², so 105 kg or 5 bags of 25 kg for 21 m². Do not use sand infill if pets use the lawn. Ask the maker what infill suits your grass.

Last reviewed: 6 November 2026 · How we calculate · Report an error