Area is 2D; materials are 3D
You measured the floor in square feet; the mulch, concrete and gravel are sold in cubic feet and yards. The bridge is depth in inches ÷ 12: multiply area by that and you have cubic feet. The calculator shows yards too, since that's what the bulk order needs.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- NIST Office of Weights and Measures — the US customary and SI conversion factors used throughout this tool.
- International Code Council — the International Residential Code and International Building Code.
Figures, formulas and reference tables last verified: 19 September 2026.