Landscape fabric calculator
Enter the area and your roll size to see how the strips lay out, and how many rolls and staples to buy.
Enter your measurements
More options: Price
- Fabric laid (incl. overlaps)
- 246 sq ft (27.3 sq yd)
- Strips
- 4 × 20.5 ft long
- Roll length used
- 82 ft
- Staples
- 40 staples
10.5 ft across (with edge tuck) ÷ 3 ft rolls, overlapping 6 in = 4 × 20.5 ft long
82 ft of roll ÷ 50 ft per roll = 2 rolls
- Each roll cuts into 2 full-length strips.
- Fabric blocks weeds from below, not seeds that blow in on top. Under wood mulch it is often skipped; under gravel and rock it earns its keep.
Rolls needed by area width (length and roll size as above)
| Width | Rolls | Strips | Fabric laid (incl. overlaps) |
|---|---|---|---|
| 2 ft | 1 roll | 1 × 20.5 ft long | 61.5 sq ft |
| 3 ft | 1 roll | 2 × 20.5 ft long | 123 sq ft |
| 4 ft | 1 roll | 2 × 20.5 ft long | 123 sq ft |
| 6 ft | 2 rolls | 3 × 20.5 ft long | 185 sq ft |
| 8 ft | 2 rolls | 4 × 20.5 ft long | 246 sq ft |
| 10 ft | 2 rolls | 4 × 20.5 ft long | 246 sq ft |
| 12 ft | 3 rolls | 5 × 20.5 ft long | 308 sq ft |
Fabric goes down in strips, and each seam needs an overlap (6–12 in is common), so you use more than the bare area.
How the fabric layout works
The calculator runs strips along the longer side of the area, adds a little at each edge to tuck under edging, and overlaps neighbouring strips at every seam. Each strip after the first covers only (roll width − overlap) of new ground, which is why a 3 ft roll covering a 10 ft wide bed needs four strips, not three and a third.
strips = (width + 2 × edge − overlap) ÷ (roll width − overlap), rounded up strip length = length + 2 × edge rolls = strips ÷ strips per roll (or total length ÷ roll length)
Rolls are counted in whole, full-length strips, which can leave long offcuts. With the metric defaults — a 6 × 3 m area and 1 × 10 m rolls — each strip is 6.16 m, so a 10 m roll yields only one of them and the job takes 4 rolls. Join the 3.84 m offcuts end to end, overlapped like a seam, and 3 rolls are enough; the calculator flags this when it applies.
When fabric helps — and when it doesn’t
- Under gravel, rock and pavers: it separates the stone from the soil, so the stone doesn’t sink and the soil doesn’t work up into it. On soft clay, a woven geotextile under the base of a patio such as How many pavers for a 12×16 patio does the same job.
- Under wood mulch: mulch breaks down into soil on top of the fabric, and weeds root into that. UNH Extension and Colorado State University Extension both advise against fabric under mulch in shrub and perennial beds.
- Around perennials you want to spread: fabric stops them. Leave it out.
- Behind a retaining wall: a non-woven fabric wrapped around the drainage stone keeps soil from clogging it — see the stone quantities in How many blocks for a 40 ft retaining wall, 3 ft high.
- Under a pond liner: that is a job for pond underlayment, which is thicker and made to cushion the liner. Size it the same as the liner, as in What size liner for an 8×6 pond, 2 ft deep.
- Woven vs non-woven: woven is strong and drains well; heavy non-woven (needle-punched) resists tearing on rough stone. Thin spunbond sheets are the ones that shred in a season.
Laying tips
- Remove weeds and rake the ground smooth first — lumps and roots poke through.
- Overlap seams 6–12 in, more on slopes or under gravel, and lap uphill pieces over downhill ones.
- Pin edges and seams every couple of feet and a few staples through the middle; cut an X for each plant.
- Cover it quickly — sunlight breaks down most fabrics.
What you’ll need
- Landscape fabric (woven or heavy non-woven)Budget price
Separates stone from soil under gravel and rock. Less useful under wood mulch, which breaks down into soil on top of it anyway.
See options on Amazon (opens in a new tab) - Landscape fabric staplesBudget price
Pins fabric and edging down. Budget roughly one every few feet along seams and edges.
See options on Amazon (opens in a new tab) - Steel or aluminum landscape edgingMid-range price
Rigid edging that holds gravel and pea gravel in place and keeps a clean line against lawn.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much landscape fabric do I need for a 10 × 20 area?
With 3 ft wide fabric and 6 in seam overlaps, the 10 ft width takes four strips, each about 20.5 ft long with a little edge tuck — about 82 ft of roll, or two 50 ft rolls. A 4 ft roll needs three strips, and a 6 ft roll only two.
How much should landscape fabric overlap?
Commonly 6–12 in at seams, more on slopes or under gravel where stone can push the edges apart. Check the fabric maker’s instructions.
How many landscape staples do I need?
A common approach is one every 2–3 ft along edges and seams plus a few in the middle. A 10 × 20 ft area laid in four strips (three seams) needs about 40 at 3 ft spacing along the edges and seams.
Should I put landscape fabric under mulch?
Extension services such as UNH and Colorado State advise against it in shrub and perennial beds: mulch breaks down on top of the fabric and weeds root in it anyway, and the fabric clogs and restricts water and air. Under gravel and rock, it is useful.
Related guides
Sources
- UNH Extension — Should I use landscape fabric to keep weeds out of my perennial garden? (opens in a new tab) — Weeds root in mulch or soil that builds up on top of fabric; pores clog over time and reduce water reaching the soil.
- Colorado State University Extension — Mulching (opens in a new tab) — Black plastic and woven weed-barrier fabrics are not recommended beneath mulch in landscape beds.