Multiply length × width × depth in feet, divide by 27 for cubic yards, then multiply by 1.45 to get tons of stone dust. A 1-inch screed layer over a 12 × 10 ft patio needs about 0.37 cubic yards — roughly half a ton.
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Stone Dust Calculator Guide
Stone dust — sold under half a dozen names including screenings, quarry dust, fines, and decomposed granite fines — is the finest product to come out of a rock crusher. It packs into a smooth, hard, almost concrete-like surface, which makes it the traditional bedding for flagstone, the joint filler for dry-laid patios, and the leveling course on bocce courts and horse arenas. This calculator estimates it at 1.45 tons per cubic yard.
Because stone dust is cheap and easy to screed, it gets used in places it shouldn’t be — most controversially under interlocking concrete pavers. The guide below covers where it excels and where the industry has moved away from it.
Where Stone Dust Belongs (and Where It Doesn’t)
| Application | Verdict | Why |
|---|---|---|
| Flagstone bedding | Excellent | Molds to irregular stone bottoms and packs firm |
| Joint filler between flagstones | Excellent | Locks tight, sweeps in easily, tolerates movement |
| Path surfacing | Good | Compacts into a smooth, wheelchair-friendly surface |
| Under interlocking pavers | Avoid | Holds water and pumps through joints; ICPI specifies concrete sand |
| Structural base layer | Avoid | No coarse aggregate — strength must come from crusher run below |
How Thick Should Stone Dust Be?
Keep it to about 1 inch as a bedding or leveling course — the calculator defaults to exactly that. Fine material settles unevenly in thick layers, so depth beyond an inch buys you problems, not strength. The structure underneath should be 4 inches of compacted crusher run; stone dust is the finish carpenter, not the framer.
For a typical flagstone patio, that means two orders: base stone by the ton, and roughly a third as much stone dust. Screed the dust dead level, set each flagstone with a rubber mallet, then sweep more dust into the joints and mist with water — it will tighten into place over the first few weeks.
Stone Dust vs Sand Under Pavers
The short version of a long argument: manufactured interlocking pavers want washed concrete sand beneath them because it drains freely and lets each unit seat independently. Stone dust holds moisture and can pump up through joints under traffic. Natural flagstone, with its irregular bottoms, wants stone dust for exactly the opposite reason — it molds and grips. Match the bedding to the paving and both camps are right.
Frequently Asked Questions
What is stone dust?
Stone dust — also sold as screenings, quarry dust, or fines — is the powder-to-sand sized byproduct of crushing rock. It compacts into a hard, smooth layer, which makes it popular for leveling under pavers and filling between flagstones.
Is stone dust better than sand under pavers?
Most paver manufacturers (and the ICPI) specify washed concrete sand for the 1-inch bedding layer because it drains freely. Stone dust can hold water and pump up through joints, so use it for flagstone bedding and joint filling, and sand for interlocking paver beds.
How thick should a stone dust layer be?
Keep leveling layers to about 1 inch — thicker layers of fine material settle unevenly. The structural strength should come from the 4-inch compacted crusher run base beneath it, not the dust itself.
How much does stone dust weigh?
Stone dust weighs about 1.45 US tons per cubic yard, similar to sand. It is sold loose by the yard or ton at stone yards, and in 50 lb bags at home centers for small repairs.