Landscape fabric is laid in strips the width of the roll, side by side, and every strip is a piece cut from a roll. The roll count follows from how many strips the bed needs and how many whole strips each roll can supply.
n strips cover n × roll width − (n − 1) × overlap
Strips = the smallest n that covers the bed width
Strips per roll = roll length ÷ strip length, rounded down
Rolls = strips ÷ strips per roll, rounded up
A 30 × 10 ft bed
The bed is 300 sq ft. With a 3 ft × 50 ft roll and a 6 in overlap, the strips can run two ways. Running along the 30 ft length, each strip is 30 ft long, so a 50 ft roll yields one, and the bed needs 4 strips ÷ 1 per roll = 4 rolls. Running across the 30 ft width, each strip is only 10 ft, so one roll yields five, and the bed needs 12 strips ÷ 5 per roll = 2.4 rolls.
Worked example 30 × 10 ft bed, 3 × 50 ft roll, 6 in overlap, strips along the width
| Material | Calculated | Buy |
|---|---|---|
| Landscape fabric3 ft × 50 ft roll, 6 in overlap, strips along the width | 12 strips ÷ 5 per roll = 2.4 rolls | 3 rolls |
“Best of the two” in the planner compares these two simple layouts, where every strip is a single piece, and picks the one that needs fewer rolls: here 3 rolls. That is not a full cut plan, and it does not model seams or cut-outs.
Why not area ÷ roll area
The bed is 300 sq ft and a roll is 150 sq ft, so dividing the areas says 2 rolls. The strip method says 3 rolls. The area method ignores two things: the overlap uses up some of every strip, and the part of a roll shorter than a strip cannot be used. Here the overlap alone takes the strips across the 30 ft side from 10 to 12, and running them along the length leaves most of each roll unused.
This example assumes
- 3 ft × 50 ft roll and 6 in overlap are example values: use your fabric’s
- One rectangular bed, with every strip cut as one piece
- No allowance beyond the overlap
If a strip is longer than the roll
A layout is unavailable when one strip would be longer than the roll. If the other direction works, the planner uses it; if neither does, it says a one-piece layout is not possible, because seams are outside what this version models. A longer roll, or splitting the bed into sections, is the way around that.
What to enter
Take the roll width, roll length and overlap from the fabric’s label and instructions. The overlap is a product instruction and is covered in how overlap changes the roll count. If you are covering the fabric afterwards, how much mulch you need is the next quantity.
What changes the estimate?
- Roll width and length
- The overlap in the fabric’s instructions
- Which way the strips run, which sets strip length
- Whether the bed is a single rectangle