Patio/Sidewalk Stone Enter the approximate length and width of your patio or sidewalk then Calculate. The calculator will tell you approximately how many tons of stone you'll need to build your project (based on typical coverage of 100 sq. ft./ton). Width (Feet) Length (Feet) Approx. tons of material required: Note: coverage will vary slightly depending on the product. Please see product listings for actual coverage amounts. To calculate the amount needed for products with coverage other than 100 sq. ft./ton, use this formula: length x width / coverage.