Wall: Stack Stone Calculate the amount of stone you'll need to build a freestanding wall (such as a retaining wall) or to cover an existing wall (such as a fireplace). Enter the length and height of the wall you are building, then click Calculate. The calculator will tell you approximately how many tons of stone you'll need to build (or cover) your wall (based on typical coverage of 25 sq. ft./ton). Length (Feet) Height (Feet) Approx. tons of material required: Example: 1 ton of stack stone will build a garden wall approximately 1 ft. high by 25 ft. long. The same amount would cover a fireplace wall of 5 ft. by 5 ft. 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 25 sq.ft./ton, use this formula: length x height / coverage.