Mulch Calculator
Length (feet)
Width (feet)
Depth (inches)

For amounts 2 through 5, round up one whole number. (Example: 2.4 = 3)
For amounts 6 & up, round up two whole numbers. (Example: 8.4 = 10)

The math for coverage of area is "Length x Width / 27 / 12 x Depth"
Remember that this is only an estimate.