Divide border length by stone length plus gap: a 40-foot border edged with 12-inch stones and 1-inch gaps needs 37 stones. Order 5–10% extra to cover cuts, splits, and the odd stone that refuses to sit right.
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Stone Edging Calculator Guide
Edging is the one stone project you buy by the piece, and the arithmetic is a division problem: border length divided by the space each stone occupies, which is its length plus the gap you leave beside it. This calculator does exactly that — enter the run of the border, the stone length, and the gap, and it returns a count. A 40-foot bed line with 12-inch stones and 1-inch gaps works out to 37 stones; butt them tight and it becomes an even 40.
The count is the easy half. The decisions that make edging look deliberate — gap or no gap, laid flat or stood on end, floated on soil or set in a trench — change both the number you order and how many seasons the border survives, so settle them before the division.
How Many Edging Stones per Border?
| Border length | 12-in stones, 1-in gaps | 18-in stones, 2-in gaps | 8-in setts, butted tight |
|---|---|---|---|
| 25 ft | 24 | 15 | 38 |
| 50 ft | 47 | 30 | 75 |
| 75 ft | 70 | 45 | 113 |
| 100 ft | 93 | 60 | 150 |
Add 5–10% on top of the count for splits, cuts at corners, and the culls every pallet hides. Curves quietly inflate consumption too: on a tight bend the gaps fan open along the outside face, so a serpentine bed line uses a handful more stones than the same length pulled straight.
Trench Setting Beats Surface Laying
Stones balanced on top of the soil become a scattered rockery within two seasons — mowers nudge them, frost tilts them, mulch buries them. The durable method is a trench: dig a channel one third to one half the stone height deep, spread 2 inches of stone dust in the bottom, and bed each stone into it with a mallet, checking the tops against a string line. The buried portion braces the stone against lawn pressure from one side and bed material from the other.
Height comes from orientation. Laid flat, a 12-inch stone gives length and stability; stood on end as a soldier course, the same stone yields 7–8 inches of visible border but occupies only its width along the run — recalculate with width as the length and expect the count to roughly double. For a mow-over edge, set the stones flush with the turf so the mower deck rides across; for gravel containment, keep them proud by an inch.
Edging usually arrives as the finishing touch on a larger job: the walkway stone calculator fills the path the border contains, and the gravel calculator covers the beds behind it. Count the border first, though — the containment going in before the loose stone is the difference between a crisp line and a cleanup.
Frequently Asked Questions
How many edging stones do I need per foot of border?
With 12-inch stones butted tight you need one per foot; add a 1-inch gap and it drops to about 0.92 stones per foot. Curved borders consume slightly more because the gaps open on the outside of every bend.
How deep should stone edging be set?
Bury a third to half of each stone’s height in a trench so lawn and bed pressure cannot tip it. A 2-inch bed of compacted stone dust in the trench bottom lets you level each stone and keeps the course from sinking unevenly.
Should edging stones touch or have gaps?
Butt them tight where the border must hold back mulch or gravel — gaps leak material. Leave deliberate 1–2 inch gaps only for decorative borders in lawns, where a little separation reads as intentional rhythm rather than shrinkage.
Can I set edging stones on end for more height?
Yes — the soldier course, stood vertically, turns a 12-inch stone into 7–8 inches of visible border. Because less length faces the run, recalculate with the stone’s width as its length; the count roughly doubles.