How to calculate it yourself
Bags needed = (cubic yards × 27) ÷ bag size in cubic feet, rounded up. Example: 1.5 yd³ ÷ 2 ft³ bag = (1.5 × 27 ÷ 2) = 21 bags.
Common scenarios
Small flower bed (½ yard)
0.5 yd³ × 27 ÷ 2 ft³ ≈ 7 bags. Buy retail — not worth delivery.
Medium project (2 yards)
2 × 27 ÷ 2 ft³ = 27 bags retail, or one bulk delivery. At ~$5/bag vs ~$35/yard delivered, bulk wins.
Whole-property refresh (5 yards)
Always buy bulk. 5 yd³ in bags would be 67–68 bags — nearly a pickup truck full.