Landscape Fabric Calculator

How it works

The calculator lays strips of fabric along the bed, overlapping them at the seams, adds the edge tucked into the soil on each side, and divides the total length by the length of one roll.

Covered width = Bed width + 2 × Edge tuck
Covered length = Bed length + 2 × Edge tuck
Strips = ⌈ (Covered width − Overlap) ÷ (Roll width − Overlap) ⌉
Pieces per strip = ⌈ (Covered length − Overlap) ÷ (Roll length − Overlap) ⌉
Fabric length = Strips × (Covered length + (Pieces − 1) × Overlap) × (1 + Extra ÷ 100)
Rolls = ⌈ Fabric length ÷ Roll length ⌉
Staples = ⌈ (2 × (Length + Width) + (Strips − 1) × Length + (Pieces − 1) × Width) ÷ Spacing ⌉

⌈ ⌉ means rounding up. Strips and pieces are whole numbers; if one roll width already covers the bed, there is one strip and no seam.

Why area ÷ roll area is not enough

A 20 × 6 ft bed has 120 sq ft, and a 3 × 50 ft roll has 150 sq ft – so one roll looks enough. But two 3 ft strips side by side with a 6 in overlap cover only 5.5 ft, so the bed needs three strips of 20 ft: 60 ft of fabric, which is two rolls. Overlaps, tucked edges and whole strips are what the area shortcut misses.

Roll sizes

Landscape fabric is sold by width × length. DeWitt, for example, lists its Weed-Barrier PRO in 3′ × 50′ and 3′ × 100′ retail rolls and bulk rolls up to 12′ × 300′; GROUNDTEX lists rolls from 1.0 m × 50 m. Those are the example sizes here – replace them with the roll you are pricing. A roll as wide as the bed avoids seams altogether, so check whether a wider roll is available.

Overlap and edges

Seams are where weeds find a way through, so the strips overlap. DeWitt’s installation guide says any overlap should be at least 6 to 8 inches and to leave extra fabric along the border; GROUNDTEX says joints should overlap by at least 100 mm and that edges are best secured by trenching the fabric 100–150 mm into the soil. The overlap is taken off every roll width except one, and the edge tuck is added to both sides and both ends of the bed.

Staples and pins

Fabric is held down with U-shaped staples or pins until the mulch or stone goes on. DeWitt says to secure the fabric “at regular intervals, especially along seams and edges” but gives no spacing, so this calculator asks for yours. It measures the bed perimeter, each seam and each end join, and divides by the spacing. Pins through the middle of wide strips, around plants and on slopes come on top.

Cut-outs and irregular beds

For a curved bed, enter the rectangle that encloses it – the fabric is cut to shape on site, and the offcuts are usually too narrow to reuse. Holes cut for plants are not subtracted, because the fabric is still bought by the roll.

Worked example

Common mistakes

• Dividing the bed area by the roll area. Every seam overlap and every tucked edge uses fabric, so a bed needs more than its area suggests – sometimes a whole extra strip.
• Laying strips across a long bed. Strips laid along the length need fewer seams and fewer staples.
• Forgetting the overlap where one roll ends and the next begins. The calculator adds one overlap for each end-to-end join.
• Pinning only the edges. Seams lift first; the instructions for most fabrics say to pin along the seams as well.
• Covering fabric with mulch or stone that is too thin to hold it down and hide it from sunlight. Follow the fabric maker’s guidance for the cover.

Assumptions and limits

• The bed is a rectangle. Strips run along the bed length; the roll width goes across.
• Strips = ⌈ (bed width + 2 × edge tuck − overlap) ÷ (roll width − overlap) ⌉, or 1 when one roll width covers the bed.
• When a strip is longer than a roll, the pieces are joined end to end with the same overlap.
• Rolls are the total fabric length divided by the roll length, rounded up. Offcuts are assumed to be reused; with many short strips you may need an extra roll.
• Staples cover the bed perimeter, the side seams and any end joins at the spacing you enter. Pins in the middle of wide strips are not included.

Frequently asked questions

Sources

• Weed-Barrier PRO Black (3 oz) – product page — DeWitt Company. Landscape fabric sold in retail rolls of 3′ x 50′ and 3′ x 100′, and bulk rolls up to 12′ x 300′ (US roll default 3 ft × 50 ft).
• Installing Weed Barrier Fabric – installation guide — DeWitt Company. "Lay fabric making sure any overlap is at least 6 to 8 inches and leave extra fabric along border"; secure with anchor pins "at regular intervals, especially along seams and edges" (US overlap default 6 in).
• GROUNDTEX Ground Cover Fabric – installation guidelines and product sizes — Product That Works (GROUNDTEX). "Ensure joints are overlapped by a minimum of 100mm"; edges are best secured by trenching "the fabric 100-150mm into the soil"; rolls 1.0 m × 50 m and wider (metric defaults: 1 m × 50 m roll, 100 mm overlap, 100 mm edge).
• PAV-TEC-002-22 – Construction of Interlocking Concrete Pavements — Concrete Masonry & Hardscapes Association (formerly ICPI). "Sidewalks, patios and pedestrian areas should have a minimum base thickness (after compaction) of 4 in. (100 mm) over well-drained soils"; "Bedding sand should be spread and screeded to an uncompacted nominal 1 in. (25 mm) thickness."
• NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.

Method reviewed November 4, 2026