Formula
The lawn grows by the edge allowance on every side. Strips run one way; the number of strips is the width across them divided by the roll width, rounded up.
Each strip is as long as the lawn in that direction, rounded up to 0.1 m. The order is strips times strip length.
Both directions are worked out and the one with less grass is kept. Seams are strips minus one; joining tape is seams times strip length.
Worked example
With 50 mm at each edge, strips across the width cover 6.10 m across: 2 strips of 4 m roll, each 4.6 m long.
That is 9.2 m of roll, 36.80 m². The other direction would need 48.80 m².
Assumptions
All strips run the same way so the pile faces one direction.
A narrower last strip is still cut from a full-width roll, so its offcut is counted as bought.
Sub-base, sand and weed membrane are not counted. The Tonnes page converts a sub-base depth to bulk bags.
Checked
Checked 11 November 2026. Namgrass and B&Q list artificial grass in 2 m and 4 m widths; Namgrass cuts to 10 cm. Australian specialists list 2 m and 4 m widths, and Bunnings lists Tuff Turf at 1.8 m wide by the lineal metre.