Decorative Stone Calculator
Calculate decorative rock for beds and borders — tons for delivery or bags — with the density matched to pea gravel, river rock or large stone.
Stone size sets the density
A cubic yard of decorative rock does not weigh a fixed amount — the smaller the stone, the tighter it packs and the heavier the yard. Pea gravel runs about 1.5 tons per cubic yard, mid-size river rock about 1.4, and big open stone with air between the pieces about 1.25. This calculator matches the density to the stone you pick, then answers in tons for the delivery truck and 0.5 cu ft bags for small beds.
Volume = area × depth · Tons = cubic yards × density for your stone size
Example: a 10 × 10 ft bed, 3 in deep in river rock, is 25 cu ft (0.93 cu yd) — 1.43 tons with the 10% allowance in, or 55 bags.
| Stone | Typical size | Density (tons per cu yd) |
|---|
| Pea gravel | 3/8 in | ≈ 1.5 |
| Crushed decorative stone | 3/4 in | ≈ 1.45 |
| River rock | 1–2 in | ≈ 1.4 |
| Large rock, small boulders | 4 in and up | ≈ 1.25 |
Depth guidance: 2 in is the minimum that hides the ground or fabric; 3 in is the finished look most people picture, and it is what paths and beds around stepping stones want. Stone settles and migrates — a bed at 3 in this spring reads 2.5 in by autumn, which is precisely what the waste allowance quietly covers.
Frequently asked questions
How many bags equal a ton of decorative stone?
A 0.5 cu ft bag of river rock weighs about 50 lb, so roughly 40 bags make a ton. Past about half a ton, bulk delivery wins on price by a wide margin — bags are for topping up and small beds.
Will 2 inches of stone stop weeds?
Stone alone does not stop weeds — landscape fabric under it does the blocking, and the stone's job is to shade and protect the fabric. Keep the full 2–3 in depth: thin stone over fabric shows the fabric and weeds find the light gaps.
Does river rock stay in place on a slope?
Round stone rolls and migrates; on any real slope, crushed angular stone locks together and stays. The density difference between them is small — the shape difference is the one that matters.
How is decorative stone priced at the yard?
By the ton or by the cubic yard (a 'scoop' is usually a yard or half-yard). When comparing suppliers, convert with the density for your stone size — a cheap ton of big open rock covers noticeably less ground than a ton of pea gravel.
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