| Scenario | Shape | Dimensions | Quantity | Overlap | Extra | Total needed | Roll length | Rolls |
|---|---|---|---|---|---|---|---|---|
| Raised bed | Rectangle | 2.0 m × 1.2 m | 1 | 5% | 0.10 m | 6.40 m | 10.0 m | 1 |
| Herb circle | Circle | Diameter 1.5 m | 2 | 7% | 0.20 m | 10.29 m | 5.0 m | 3 |
| Polygon bed | Polygon | 6 sides, 1.0 m each | 1 | 10% | 0.00 m | 6.60 m | 3.0 m | 3 |
- Rectangle: Perimeter = 2 × (Length + Width)
- Circle: Perimeter = π × Diameter
- Regular polygon: Perimeter = Sides × Side length
- Irregular: Perimeter = Sum of segment lengths
- Quantity: Base total = Perimeter × Quantity
- Allowances: Total needed = Base total × (1 + Overlap/100) + Extra length
- Rolls: Rolls required = ceil(Total needed ÷ Roll length)
- Select your bed/plot shape and preferred unit.
- Enter dimensions for that shape, then set quantity.
- Add overlap percent for joins, corners, and trimming.
- Add extra length for gates, anchors, or mistakes.
- Enter roll length to estimate roll count.
- Optionally enter costs for budgeting and comparison.
- Press Calculate, then download CSV or PDF records.
Barrier planning for bed protection
Slug barriers work best when the protected edge is continuous. This calculator converts your bed or plot outline into a perimeter, then adds practical allowances. Use it for copper tape, mesh edging, salt-free strips, or physical borders that discourage crossing. A defined plan reduces gaps that slugs exploit after watering or overnight feeding.
Measuring layouts with consistent units
Select meters or feet and keep every input in that unit. For rectangles, measure the outside edge you will wrap, not the planting area. For circles, measure diameter through the center. For regular polygons, confirm that each side is equal. For irregular beds, walk the boundary and record each straight segment.
Allowances for joins, corners, and terrain
Real installations need overlap at seams and extra length for corners, posts, and tensioning. Overlap percent covers repeated joins around the perimeter, while extra length is a fixed reserve for trimming, repairs, and alignment. If your ground is uneven, increase overlap slightly to maintain contact and prevent lifted edges.
Choosing rolls and budgeting accurately
Supplies are often sold in rolls, so the tool converts total required length into an integer roll count using ceiling rounding. Enter roll length to match the product packaging. Optional pricing fields estimate cost by linear length or by roll, helping compare alternatives such as copper versus fabric skirts. Use the higher estimate when both are provided. For multiple beds, set quantity to scale materials without repeating measurements. If beds differ, calculate each shape separately and sum totals. Document results using the download buttons so purchasing, installation notes, and seasonal maintenance stay consistent across your garden plan.
Installation checks to keep slugs out
After purchase, dry-fit the barrier around the bed, verify the measured perimeter, and confirm overlap at every joint. Keep the barrier clean, especially for conductive materials, and avoid bridges made by mulch, leaves, or irrigation lines. Recheck after heavy rain, soil settling, or harvest activities to maintain a reliable perimeter defense.
What overlap percent should I use?
Use 5–10% for most borders. Increase to 12–15% when you expect many seams, sharp corners, or uneven soil. Overlap helps keep joints closed after watering and seasonal settling.
Should I measure inside or outside the bed?
Measure the outside edge that the barrier will wrap. If the barrier sits on the ground around the frame, outside dimensions are correct. Inside measurements can undercount and leave exposed entry points.
How do I handle an irregular garden shape?
Choose the irregular option and enter each straight segment you can measure. Walk the boundary, record lengths, and include every edge you will protect. Add overlap to cover small curves and transitions.
Why does the calculator round rolls up?
You cannot buy fractional rolls. The roll count uses ceiling rounding so you always have enough material to complete the loop, make overlaps, and correct small cutting errors without leaving a gap.
Can I calculate multiple different beds?
Yes. Run the calculator for each bed type and note the total needed. Add the totals together for purchasing. Use CSV or PDF downloads to keep a clean record for repeat builds or replacements.
What if my barrier is sold by packs, not rolls?
Enter the pack length as roll length. If a pack contains several pieces, sum their usable length. The roll count then becomes the number of packs you need to meet the total required length.