How this calculator works
Each section's area is its width times its length in inches, divided by 144 to convert to square feet (144 square inches = 1 square foot). The grand total is the sum of every section. To estimate slabs, the tool computes the area of one slab, multiplies by your usable-yield percentage to allow for kerf, edge polishing, off-cuts, and grain, then divides your total area by that usable slab area and rounds up.
It's a fast sanity check, not a cut list. Real slab count is decided by how the pieces actually nest onto the slab — a tight layout can fit a job on one slab where a loose one needs two. For a precise number, draw the real shapes and let the layout prove what fits.
Square footage FAQ
How do I calculate countertop square footage?
Measure each section's width and length in inches, multiply them, and divide by 144 to get square feet. Add every section together for the total. For a typical 25.5"-deep run that's 120" long, that's 120 × 25.5 ÷ 144 ≈ 21.25 sq ft. Break L-shapes and islands into separate rectangles so you don't overcount the overlap at a corner.
How many square feet are in a slab?
It depends on the slab. A common quartz or granite slab runs roughly 120–130" wide by 60–65" tall, which is about 50–58 sq ft of gross stone. You never get all of it as countertop, though — kerf, edge allowances, squaring the rough factory edge, and off-cuts mean usable yield is typically well under 100%, which is why this tool lets you set a usable-yield percentage.
Why is my real area less than width times length?
Width × length is the bounding box — the rectangle that surrounds the piece. Any shape that isn't a plain rectangle (an L, a U, a clipped corner, a curve) has less stone inside that box. Quoting off the box quietly inflates the material. SlabOS measures the exact drawn polygon, so the area reflects the shape you actually cut.
Does total square footage tell me how many slabs I need?
Only roughly. Area gives you a lower bound, but slab count is really a layout problem: two jobs with identical square footage can need a different number of slabs depending on how the pieces fit, the grain direction, and where seams land. This estimator divides by usable slab area to ballpark it — for the real number, nest the actual pieces onto the slab.
What's the standard countertop depth?
Standard kitchen countertop depth is about 25.5" including a typical 1.5" overhang past a 24"-deep base cabinet. Islands and bars vary widely. If you're measuring an existing top, measure the actual depth rather than assuming — and enter it as the width or length for each section here.
Quote the real shape, not a box
Book a demo and we'll draw one of your jobs in live 2D and 3D, price it from your real slab costs, and nest it onto a slab so you can see exactly how much stone — and how many slabs — it actually takes.