How to calculate it yourself
Cubic feet of soil needed = (length × width × depth) all in feet. Cubic yards = cubic feet ÷ 27. For a 4×8 raised bed at 12 inches deep: 32 ft³ = 1.18 yd³.
Common scenarios
Raised garden bed (4×8 ft × 12 in deep)
32 ft³ of soil. That is 1.2 yd³ in bulk, or 32 bags of 1 cu ft potting mix at retail prices.
Top-dress a lawn (1,000 ft² × ½ in)
42 ft³ = 1.5 yd³. Bulk delivery makes sense; bagged would be ~42 bags of 1 cu ft.
Fill a planter (2×3 ft × 12 in deep)
6 ft³ = 0.22 yd³. Bagged is the right call: 6 bags of 1 cu ft.