Mulch cubic yards, bags & coverage — area × depth ÷ 324, and 13.5 bags per yard

Two steps to an order. Volume: cubic yards = area(ft²) × depth(in) ÷ 324 (324 = 12 in/ft × 27 ft³/yd³). Format: one cubic yard (27 ft³) = 13.5 of the 2-ft³ bags. Coverage is volume ÷ depth, so a deeper layer covers less — 324 ft² at 1″ down to 81 ft² at 4″. Add ~7.5% for spillage.

What this diagram shows

A conversion diagram turning area and depth into a mulch order. The volume formula is cubic yards equals area in square feet times depth in inches divided by 324, where 324 is 12 inches per foot times 27 cubic feet per cubic yard, folding the inch-depth conversion straight into yards. An isometric cube shows one cubic yard as 3 by 3 by 3 feet, or 27 cubic feet, which equals 13.5 of the common 2-cubic-foot bags, drawn as a stack. Because coverage is volume divided by depth, a deeper layer covers less area per yard: one cubic yard covers 324 square feet at 1 inch, 162 at 2 inches, 108 at 3 inches, and 81 at 4 inches. Bulk is cheaper per yard for big beds; bags suit small top-ups.