How this calculator works
The calculator converts the countertop run and depth into square feet, then adds any island or peninsula area. It applies the waste allowance to produce an order area. Slabs or sheets are rounded up from order area divided by usable slab area. Edge length is estimated from the main run plus island perimeter planning allowance.
Example: a 24 ft run at 25.5 inches deep is 51.0 square feet. Add a 20 square foot island and the project area is 71.0 square feet. With 12% waste, the order area becomes 79.5 square feet, which rounds to 2 slabs at 50 square feet each.