| Bed type | Dimensions | Coverage | Waste | Approx. border length |
|---|---|---|---|---|
| Rectangle | 4 m × 2 m | 100% | 5% | ≈ 12.60 m |
| Circle | Diameter 3 m | 100% | 8% | ≈ 10.18 m |
| Oval | Major 6 m, Minor 3 m | 100% | 10% | ≈ 16.54 m |
| Polygon | Sides: 2, 2, 3.5, 3.5 (m) | 50% | 5% | ≈ 5.78 m |
| Rect. with cutout | Outer 5×4 m, Cutout 2×1.5 m | 100% | 5% | ≈ 22.05 m (with inner) |
- Rectangle: Perimeter = 2 × (Length + Width).
- Circle: Circumference = 2 × π × Radius (Radius = Diameter ÷ 2).
- Oval/Ellipse: Ramanujan approximation: π[3(a+b) − √((3a+b)(a+3b))], where a and b are semi-axes.
- Polygon (side list): Perimeter = Sum of all side lengths.
- Rectangle with cutout: Total = Outer perimeter + (optional) Inner perimeter.
- Coverage: Adjusted length = Perimeter × Coverage factor.
- Waste: Final length = Adjusted length × (1 + Waste%/100).
- Rolls needed: Rolls = ceil(Final length ÷ Roll length).
- Stakes: Stakes ≈ ceil(Final length ÷ Stake spacing).
- Select the bed shape that matches your layout.
- Pick units, then enter all dimensions in that unit.
- Choose coverage if you will edge only certain sides.
- Add waste for overlaps, trimming, and curved sections.
- Optionally enter roll length to estimate pieces to buy.
- Optionally enter stake spacing for a peg count estimate.
- Optionally enter a unit price to project edging cost.
- Press calculate, then export your results if needed.
Why border length matters for healthier beds
A continuous border reduces soil spill, keeps mulch in place, and creates cleaner irrigation zones. Most edging failures come from underestimating length at corners, curves, and overlaps. This calculator converts your shape into a perimeter value, then applies coverage and waste. In practice, adding 5–10% waste covers trimming and end-to-end joins.
Typical edging materials and roll lengths
Flexible plastic or rubber edging is commonly sold in 10–30 meter rolls (or 20–100 feet). Rigid metal or composite pieces are often 1–2 meter sections that overlap by 2–5 cm per joint. If your edging requires overlap, treat the overlap as “waste” so the final purchase length stays realistic. For stone or brick borders, length planning supports accurate counts and reduced returns.
Coverage choices for beds against walls or fences
Many beds only need edging on exposed sides. Use 50% coverage for a bed centered on a straight boundary, or enter a custom percentage for odd placements. As a rule, corner-heavy layouts benefit from higher waste, while long straight runs can use less. If you plan a gate or access gap, reduce coverage slightly to reflect the opening.
Stake spacing and stability data
Peg spacing affects border performance. Light flexible edging often holds well with stakes every 0.5–1.0 meters, while tight curves may need 0.25–0.4 meters. Taller edging and soft soils usually require closer spacing. The stake estimate here uses your spacing against the final waste-adjusted length to help you buy enough pegs.
Example data you can copy
Use these examples to validate your inputs: Rectangle 3.0 m × 1.2 m, 100% coverage, 7% waste → about 8.99 m. Circle diameter 2.4 m, 100% coverage, 10% waste → about 8.29 m. Oval major 4.0 m, minor 2.0 m, 100% coverage, 8% waste → about 10.47 m. Adjust waste upward when you expect overlaps or tight bends.
FAQs
1) What waste percentage should I use?
For most beds, 5–10% works well. Use 10–15% for many corners, overlaps, or tight curves. If you are very precise with rigid pieces, 3–5% may be enough.
2) How do I measure an irregular bed?
Break it into straight segments and measure each segment length, then enter them as a polygon side list. For smooth arcs, approximate with short segments to improve accuracy.
3) Does the calculator include overlaps between edging pieces?
Not directly. Add overlap allowance into the waste percentage. For example, if each joint overlaps 3 cm and you have many joints, increasing waste by a few percent usually covers it.
4) Why is oval perimeter an approximation?
An ellipse does not have a simple exact perimeter formula. This tool uses a high-accuracy Ramanujan approximation, which is very close for typical garden bed proportions.
5) When should I use custom coverage?
Use custom coverage when edging only part of the bed, such as three sides along a fence, or when leaving an access gap. Enter the percentage of the perimeter you will actually edge.
6) How many stakes should I plan for?
Common spacing is 0.5–1.0 m for straight runs. Use closer spacing for curves and soft soil. The estimate rounds up so you are less likely to run short during installation.
7) Can I use this for stone or brick borders?
Yes. Use the border length with your unit size to estimate counts. For example, with 20 cm bricks, divide total length by 0.2 and add extra for cuts and breakage.