Same formula, different weights
Every bulk material starts the same way: length × width × depth gives cubic feet, and dividing by 27 gives cubic yards. What changes is weight. A cubic yard of mulch weighs well under a ton, crushed stone about 1.4 tons and concrete about 2 tons. Use the cubic yard calculator for volume alone, or a material page for tons and bags.
Bulk or bagged?
One cubic yard is 54 bags of 0.5 cubic feet or 13.5 bags of 2 cubic feet. Past about one yard, bulk delivery is usually cheaper per yard, even after the delivery fee.