Every calculator on this site runs the same formula and follows the same sourcing rules. This page explains both, so you can judge the numbers instead of just trusting them.
We compute volume in cubic feet first: area (ft²) × depth (in ÷ 12). That converts to cubic yards by dividing by 27, since one cubic yard is 3 ft × 3 ft × 3 ft. A waste percentage — to cover spillage, an uneven sub-base, and settling — is applied to the volume before anything else is derived from it. Tons come from multiplying the waste-adjusted cubic yards by the material’s density. Bag counts and truckloads are simple divisions of the waste-adjusted volume by a bag’s yield or a truck’s capacity, rounded up, since a partial bag or truckload still has to be bought or driven.
Density — tons per cubic yard — is the number that turns a volume into a weight, and it’s also the number most calculators get sloppy about. We don’t accept a generated or estimated figure for any material. Every density value on this site is backed by at least two real, cited sources: a named supplier’s published figures, a state or federal DOT specification, or both. Where those sources disagree — which they often do, because density depends on moisture, gradation, and compaction — we show the full range next to the number we use for the headline estimate, rather than presenting false precision.
Even with good sources, no calculator can know the exact material in a specific supplier’s yard on a specific day. Moisture content alone can shift weight by 10% or more. Treat every result here as a planning estimate — order slightly over rather than under, and confirm the density figure with your supplier before committing to a large or expensive load.