River rock in tons, and square feet per ton

Between about 116 and 29 square feet, depending entirely on the stone size. A ton is roughly 19 cubic feet of loose rock at 2,800 lb per cubic yard, and dividing that by the depth gives the coverage: 116 sq ft for 3/4 to 1 in laid two inches deep, 77 sq ft for 1 to 3 in at three inches, 46 sq ft for 3 to 5 in at five inches, and 29 sq ft for 5 to 8 in at eight inches. That is a fourfold spread from one input, and it is the single number people get wrong when they price two sizes against each other by the ton.

As deep as the stone is tall, and no deeper, for anything that is meant to read as a covered surface. Depth on a decorative bed is not a design choice but a consequence: you cannot lay a five-inch stone three inches deep without leaving fabric showing between the pieces, and there is nothing to gain by doubling a layer that is already opaque. The exception is a dug application — a French drain, a dry well, a bedding layer around pipe — where the depth is whatever the excavation is and the stone is filling a volume rather than dressing one.

Mostly 1 to 3 in through the channel, with a scattering of 3 to 5 in and a few larger placed stones to break the line up. A creek bed done entirely in one size looks like a trench full of gravel, and one done entirely in large stone has gaps you can turn an ankle in. The small material also stays put in a downpour, which is the actual function: anything below about an inch will be somewhere else after the first storm the bed was built to carry.

More than the bed area, because every seam laps the one beside it by six inches. That overlap comes off the usable width of every roll, so a four-foot roll only puts three and a half feet of ground under stone and a three-foot roll only two and a half. Buying to the label width is how people end up one strip short at the far side of a bed. This page counts the strips across the narrow dimension, multiplies by the run and converts that into 100 ft rolls.

For two or three seasons, then it becomes a seed bed itself. What grows through rock is rarely coming up from beneath: it is windblown dirt and leaf litter settling into the gaps between stones and forming exactly the thin, well-drained layer that weeds like. Fabric underneath delays it by stopping perennial roots pushing up, and it does nothing about the debris arriving from above, which is why the maintenance job on a rock bed is blowing it out rather than pulling from it.

It lasts indefinitely and it feeds nothing, which is the trade in one sentence. Organic mulch breaks down into the soil and has to be topped up, and that decomposition is the point for a planting bed. Stone never needs replacing, but it also radiates absorbed heat into whatever is growing next to it, works its way permanently into the soil surface, and cannot be dug through when the planting changes. It suits foundation strips, side yards and drainage lines far better than it suits a perennial border.

Hard enough to be worth pricing before it goes down. A 200 sq ft bed of 1 to 3 in stone laid three inches deep is about 2.6 tons that has to leave by shovel and wheelbarrow, and once it has been in place a few years the bottom layer is set into the soil and the fabric beneath it has usually torn into pieces around it. Rock is the least reversible decision available in a garden bed, which is the strongest argument for measuring carefully rather than ordering an extra ton to be safe.