Formulas for calculating mulch coverage
Every 100 sq ft of bed area (10x10) with 2" coverage requires 9 bags
Every 100 sq ft of bed area (10x10) with 3" coverage requires 13 bags
Every 100 sq ft of bed area (10x10) with 4" coverage requires 17 bags
Each Bag = 2 cu ft, 14 bags = 1 cu yd and is 28 cu ft
Mulch should be 3" minimum to keep ground moist and weeds out, 4" recommended by landscapers