Landscape Fabric Calculator

How it works

Fabric is laid in strips running the length of the bed. Each seam overlaps the previous strip, so every strip after the first adds only the roll width less the overlap. A bed no wider than the roll takes one strip; a wider bed takes (bed width − overlap) ÷ (roll width − overlap) strips, rounded up. The strips times the bed length is the linear footage, and dividing by the roll length, rounded up, gives the rolls.

Staples are counted in three groups: around the bed's perimeter at the edge spacing, along each seam between the two end edges at the same spacing, and on a square grid across the open fabric inside the edges. With the grid spacing equal to the edge spacing and a single strip, the count is exactly the points of one grid covering the bed. Packs are the staple count divided by the pack size, rounded up.

Formula

overlap o (ft) = overlap (in) ÷ 12
strips     = 1 if bed width ≤ roll width, else ⌈ (bed width − o) ÷ (roll width − o) ⌉
linear ft  = strips × bed length
rolls      = ⌈ linear ft ÷ roll length ⌉
fabric     = linear ft × roll width                  (sq ft, including overlaps)
staples    = ⌈ 2 (L + W) ÷ e ⌉ + (strips − 1)(⌈ L ÷ e ⌉ − 1) + (⌈ L ÷ g ⌉ − 1)(⌈ W ÷ g ⌉ − 1)
packs      = ⌈ staples ÷ pack size ⌉            e = edge spacing, g = grid spacing (ft)

Example

A 20 ft × 6 ft bed covered with 3 ft × 50 ft rolls overlapped 6 in needs (6 − 0.5) ÷ (3 − 0.5) = 2.2, so 3 strips 20 ft long: 60 linear ft, which is 2 rolls. The fabric laid, overlaps included, is 180 sq ft for a 120 sq ft bed.

With staples every 12 in on the edges and seams and a 12 in grid on the open fabric, that is 52 around the perimeter, 2 × 19 = 38 along the two seams and 19 × 5 = 95 in the field: 185 staples, or 4 packs of 50.

Assumptions and limitations

• The bed is a rectangle and strips run its full length. Cut-outs for plants and curved edges are not modelled; for an irregular bed, the enclosing rectangle gives an upper bound.
• A strip longer than one roll is made up from pieces of the next roll, and offcuts from one roll are used on the next strip. End-to-end joins need their own overlap, which is not added; the rolls count is the linear footage divided by the roll length.
• No extra fabric is added for tucking under edging or running up the sides of the bed.
• Staple spacings are typical figures, not a manufacturer specification. DeWitt's installation guide calls for pins "at regular intervals, especially along seams and edges" without fixing a spacing; slopes, wind and an uncovered surface call for closer spacing, while a mulch or stone cover holds fabric down. Seam staples are counted in addition to the field grid even where the two coincide.
• Product instructions for the particular fabric take precedence over the figures here.

Frequently asked questions