How much a cubic yard really covers, which mulch depth belongs where, how bulk density changes your ton price, and when bagged material beats bulk.
One cubic yard equals 27 cubic feet. Spread one inch deep it covers 324 square feet, so coverage is simply 324 divided by your depth in inches: 162 sq ft at 2 inches, 108 sq ft at 3 inches, 81 sq ft at 4 inches. Every mulch and soil quantity question is a variation on that single relationship.
Suppliers who sell by weight are selling you water as well as material. Dry shredded hardwood mulch runs about 400 to 500 lb per cubic yard; the same yard soaked after a rain can exceed 1,000 lb. Screened topsoil averages 2,000 to 2,600 lb per cubic yard. Compost lands between 800 and 1,200 lb. If a quote is per ton, ask whether the stockpile is covered.
A 2 cubic foot bag is 1/13.5 of a yard, so 13.5 bags make a yard. At $4.50 a bag that is roughly $61 per cubic yard before you have loaded anything, against $35 to $50 delivered in bulk. The crossover is usually around 8 to 10 bags: below that, bagged wins on convenience and no delivery fee; above it, bulk wins decisively. Factor a $60 to $110 delivery charge and the practical minimum bulk order of 3 yards at most yards.