How countertop square footage is measured
Countertops are quoted by the square foot of finished surface, and the arithmetic is just length × depth ÷ 144 for each run, in inches. Measure the run along the wall from end to end and use the finished depth, not the cabinet depth — a 24″ base cabinet normally carries a 25″ to 26″ top once you allow for the overhang past the door fronts and the small gap behind for an out-of-square wall. Where two runs meet in an L, measure one run wall to wall and start the second at the edge of the first so you don't count the corner twice. A backsplash is billed the same way: run length × splash height ÷ 144, added to the deck total.
Two things routinely make the fabricator's number higher than yours. Stone and solid-surface tops are cut from slabs, so you pay for the slab area consumed, not the area installed — an awkward layout with a lot of offcut can add meaningfully to the yield required. And most quotes carry separate line items on top of the per-square-foot material rate: sink and cooktop cutouts, edge profile by the linear foot, seaming, templating and installation. Use this calculator to establish the square footage you're buying and to compare material prices like for like, then treat the fabricator's itemised quote as the real number.
Material only. Prices vary widely by material, grade and region, and fabrication, cutouts, edging and installation are usually charged separately — get a measured quote before ordering.