Determine the square footage of your garden area by multiplying the length by the width in feet. For example, if the length is 40 feet and the width is 60 feet, the total square footage of the garden is 2,400 square feet.
Divide the square footage by 90 to calculate the number of 3.8 cubic foot compressed bales you will require to lay down 1 inch of peat moss. Using the same example -- 2,400 / 90 = 26.66 -- you will need approximately 27 large bales of peat moss.
Double the number of large bales if you wish to lay down 2 inches of peat moss.
Divide the square footage by 50 to calculate the number of 2.2 cubic foot compressed bales you will require to lay down 1 inch of peat moss. Using the same example -- 2,400 / 50 = 48 -- you will need 48 medium bales of peat moss.
Double the number of medium bales if you wish to lay down 2 inches of peat moss.