Mulch and Top Soil Calculator Mulch and Top Soil Calculator (1) Choose a type of material WOOD TOP SOIL RUBBER What kind should I choose? (2) Calculate the Area of your space Enter the length and width Ft. x Ft. = (Total Value to be shown here after multiplication) sq. ft. Enter the square footage Sq. ft. (3) Enter the material Depth How much do I need? 3 inches (recommended) inches