Artificial grass calculator: rolls, seams and infill

How it works

Enter your lawn as one rectangle or split it into non-overlapping rectangles. For an L-shaped lawn, use two rectangles. Choose whether the grass pile should run along each rectangle’s length or width so the pieces all face the same way.

The calculator lays parallel strips across each rectangle using the supplier widths 2 m, 4 m. It applies the seam overlap you enter, counts seams and adds their lengths for seam tape. It then groups compatible cut strips with the same pile direction so narrow offcuts can be reused beside another strip. It compares the total roll area required at each sourced width and selects the lowest estimate.

Enter your grass product’s infill rate. The cited supplier guidance gives 4 to 5 kg/m², the product instructions take priority. The default is the lower end of that guidance and can be edited, enter 0 if your product instructions specify no infill. Bags are rounded up to 25 kg. Pins are estimated at your entered spacing, initially 0.2 m based on supplier guidance, for exposed perimeters only.

Formula

• Lawn area

  Rectangle area = length × width

  Calculate each rectangle separately, then add the areas. Use rectangles that do not overlap.

• Strips across the lawn

  Strip count = smallest whole count where (strip widths − seam overlaps) cover the across-pile width

  The pile direction sets which side of each rectangle the strips must cover.

• Grass to buy

  Grass area = roll width × grouped cut length × (1 + waste allowance)

  Matching cuts can share a roll when they fit side by side and keep the same pile direction.

• Tape, infill and pins

  Tape = seams × seam length Infill bags = ceil(lawn area × infill rate ÷ bag mass) Pins = ceil((perimeter) ÷ pin spacing)

  Bag and pin quantities round up to whole items. Follow your grass and fixing product instructions.

Measure and plan the cuts

Measure the finished area you want the grass to cover, using metres. For an irregular lawn, sketch the outline and divide it into rectangles that do not overlap. Enter each rectangle once. A right-angle extension can be entered as a separate rectangle, the calculator sums the areas and treats each listed rectangle independently.

Artificial grass can have a visible pile direction. Decide which way it should face from the main viewing point, then keep every strip aligned that way. The length and width fields describe the sides of each rectangle, while the pile-direction choice tells the calculator which side runs along the pile. Check the direction against the roll before you order or cut.

A wider roll may reduce the number of seams but can leave more unused material. A narrower roll may fit several cut strips into the same layout. The calculator compares the total material area for the widths in the local supplier data and also considers whether compatible strips can share a roll width. Compare the listed layout and seams as well as the selected area, because a lower area may mean more joins to make and tape.

If a garden includes a tree, drain, step, curved edge or narrow passage, the rectangular estimate may not represent the final cutting plan. Sketch those details separately and ask the supplier whether offcuts from your chosen product can be reused. A product may also have a maximum order length that affects whether a long strip needs another join.

Worked examples

1. 1

   Find the lawn area

   6 m × 5 m = 30 m²

   Enter the length and width, then choose which way the grass pile should run.

2. 2

   Read the roll estimate

   2 m roll × 18 m cut length = 36 m²

   For this sample, the calculator selects this width and estimates 2 seams with 12 m of tape, before waste.

3. 3

   Split an L-shaped lawn

   4 m × 3 m + 2 m × 1 m = 14 m²

   The example groups cuts that fit on one roll and estimates 16 m² to buy. Draw the rectangles so they touch where needed but never overlap.

Assumptions and limits

UK supplier examples in this estimate offer 2 m and 4 m wide grass. The width range on sale varies by product and supplier.

This is a planning estimate, not a cutting diagram for every supplier. It assumes pieces can be cut and paired as shown and all pieces use the same pile direction. It does not model maximum roll lengths, if a supplier cannot cut the full strip length, you may need another seam. The entered overlap must suit your grass and tape. Confirm roll widths, maximum order lengths, seam placement and cuts with your supplier before ordering.

The infill estimate uses lawn area, not extra grass bought for cuts. The pin estimate applies the entered interval to each rectangle's perimeter. It treats every rectangle edge as exposed, so it may overcount where rectangles touch. Corners, edges fixed with adhesive, obstacles, soft ground and the supplier’s fixing method can change the quantity. Waste defaults to zero because no universal allowance is published in these sources.

Frequently asked questions