How it works
The volume comes from the standard landscaping shortcut: cubic yards = (length ft × width ft × depth in) ÷ 324, where 324 is the 27 cubic feet in a yard multiplied by the 12 inches in a foot. That volume is then multiplied by the material's bulk density in pounds per cubic yard to get total weight and tons, while cubic feet divided by the bag size gives bags. Both prices are worked out side by side: cubic yards times your bulk rate, and bags times your bag price.
The Material select changes density and bag size together, and the two ends of the range are far apart. Gravel / Crushed Stone is 2,800 lb per cubic yard in 0.5 ft³ bags, Sand and Decomposed Granite 2,700, Topsoil 2,100 in 0.75 ft³ bags, Mulch 500 in 2 ft³ bags, and Playground Wood Chips just 450. Depth is the other lever and defaults to 3 inches, which suits mulch and a decorative gravel top dressing rather than a driveable base.
There is no waste or compaction allowance anywhere in the maths, and that gap is real: crushed stone and decomposed granite lose roughly 15 to 20 percent of their loose volume once plate-compacted, and mulch settles over a season. The densities are single averages, so wet mulch or damp topsoil weighs considerably more than the figure shown, which matters if you are checking a truck's payload limit. Inputs are feet and inches only, with no metric mode, and the area is treated as a plain rectangle.
Frequently asked questions
How much gravel do I need for a 20 by 10 foot area at 3 inches deep? +
That is 1.85 cubic yards, or 50 cubic feet, weighing about 5,185 pounds — roughly 2.6 tons. In 0.5 cubic foot bags it works out to 100 bags, which is exactly the point where bulk delivery becomes the sensible option.
Is it cheaper to buy mulch in bags or by the cubic yard? +
The results table prices both, using your own price per cubic yard and price per bag. As a rule, under about 2 cubic yards bags win once delivery minimums are counted; above that, bulk is almost always cheaper per unit and much faster to spread.
How many bags of mulch are in a cubic yard? +
Fourteen, using the 2 cubic foot bag size the tool assumes for both Mulch and Playground Wood Chips, since a cubic yard is 27 cubic feet. Gravel and sand use 0.5 cubic foot bags, so a yard of those is 54 bags.
Why is gravel so much heavier than mulch for the same volume? +
Density. The tool uses 2,800 pounds per cubic yard for gravel against 500 for bark mulch, a factor of more than five. That is why a single yard of stone can exceed a half-ton pickup's payload while three yards of mulch will not.
Does the calculator allow for compaction? +
No. It gives loose volume only. If you are building a compacted gravel base or a decomposed granite path, order about 15 to 20 percent more than the figure shown, because the material loses that much depth once it is plate-compacted or driven on.
