Landscape Edging Calculator: How Much Edging for Your Garden Bed

Enter the length and width of your garden bed in feet and press Calculate. That is all most people need: the calculator assumes a rectangular bed edged on all four sides, adds 10% for overlaps and cuts, and tells you how many 20 ft plastic edging rolls and stakes to buy.

Open More options if your bed is a circle, a half circle, an L shape, a single straight border, or a freeform kidney shape. You can also skip one side when the bed sits against your house or a fence, switch to metric, pick a different edging product (steel strips, concrete edger blocks or bricks), change the waste allowance, and enter a price per foot to get a cost estimate.

Landscape edging is sold by length, not by area, so the number that matters is the perimeter of your bed — the distance all the way around the edge you want to define. A 10x20 bed covers 200 square feet but needs only 60 linear feet of edging, which is why an area or mulch figure will not help you here.

The perimeter depends on shape. Rectangles and L shapes are simple sums of their sides. Circles use the circumference formula. Kidney beans, wavy borders and island beds don't follow a neat formula, so the most accurate method is to lay a garden hose or rope along the planned line, mark it, then straighten it out and measure it with a tape.

You always buy a little more than the perimeter. Coil edging needs a few inches of overlap at every joint, steel strips overlap or slot together, and every corner or curve costs some material when you cut. A 10% allowance covers most beds; go to 15% for tight curves or many separate sections.

Rectangle or square: Perimeter = 2 × (Length + Width)
Bed against a house (skip one side): Perimeter = 2 × (Length + Width) − the skipped side
L-shaped bed: Perimeter = 2 × (Overall length + Overall width) — the notch does not change the total for a right-angled L
Straight run: Perimeter = Length
Circle: Perimeter = π × Diameter
Half circle (curve only): Perimeter = π × Diameter ÷ 2

Edging to buy = Perimeter × (1 + allowance %)
Rolls or pieces = Edging to buy ÷ piece length, rounded up
Stakes (coil edging) = Edging to buy ÷ 3 ft, rounded up

How much edging for a 10x20 bed? Perimeter = 2 × (20 + 10) = 60 ft. Add 10%: 60 × 1.10 = 66 ft. With 20 ft rolls, 66 ÷ 20 = 3.3, so buy 4 rolls. Stakes every 3 ft: 66 ÷ 3 = 22 stakes.

How many feet of edging for a 10 foot circle? Circumference = π × 10 = 31.4 ft. With 10% extra that is 34.6 ft — 2 rolls of 20 ft edging and 12 stakes.

A 4x16 bed along the front of the house: Skip one long side: 2 × (16 + 4) − 16 = 24 ft. With 10% extra you need 26.4 ft, or four 8 ft steel strips (26.4 ÷ 8 = 3.3, rounded up).

Concrete edger blocks for a 12x12 bed: Perimeter = 48 ft, plus 10% = 52.8 ft. Each 16 in block covers 1.33 ft, so 52.8 ÷ 1.333 = 39.6 → 40 blocks.

Measure curves with a hose. For any bed that isn't a clean rectangle or circle, a hose laid on the ground gives a far better number than guessing.

Round up, never down. A leftover few feet costs less than a second trip to the store, and joints and corners always eat material.

Stake plastic edging every 3 to 4 feet, and closer on tight curves or in loose, sandy soil. Steel and aluminum strips usually ship with their own stakes, so check the package before buying extra.

Bury it deep enough. Most plastic and metal edging is set so that only about half an inch to an inch shows above the soil, which keeps mowers from catching it and stops grass roots from creeping under.

Lay coil edging out in the sun first. Warm plastic relaxes and is much easier to bend into smooth curves without kinks.