Gravel, mulch, soil, and pavers — sized by area and depth, in bags or by the yard.
Bulk material is sold by weight, delivered in a loose heap, and used as a compacted depth — three different measures of the same pile, which is why yardage estimates so often miss. These calculators keep those measures separate instead of collapsing them. Gravel, stone, and sand carry their own densities; mulch and topsoil settle differently again; paver base has to be figured at its compacted thickness, not the depth you spread. Coverage tools for sod, seed, and fertilizer work from area and application rate rather than bag-count guesswork. Where a material is commonly sold both ways, you get the cubic yards and the bag count side by side.