Kitchen & Bath
Countertop Calculator
Square footage for quartz, granite and laminate counters, including backsplash and overhang.
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About this calculator
Countertop quotes start from square footage, and the details matter: a standard 25.5 in depth, a 1.5 in overhang on exposed edges, and a 4 in backsplash strip all add area. This calculator sums each run of counter — including islands and peninsulas — into one fabrication-ready figure.
What this number means
Countertop quotes are where an honest square-footage number earns its keep: fabrication is priced by the square foot, quotes vary wildly between shops, and the homeowner who knows their kitchen is 39 sq ft — not "about 45" — can compare them on equal terms. This calculator sums every run the way a fabricator measures: each straight section at full depth, the island as its own slab piece, and the backsplash strip on top.
The cutout question is deliberately exposed. Sinks and cooktops remove stone you can see, but the slab was consumed making them — many fabricators bill the full area, some deduct. The toggle lets you see your figure both ways so a quote never surprises you.
The formula
- Each run = Length (in) × Depth (in) ÷ 144 sq in per sq ft
- Island = Island length × Island width ÷ 144
- Backsplash = Total base-run length × Splash height ÷ 144
- Total = Runs + island + backsplash − (2.3 sq ft × cutouts, only if deducting)
- Slabs ≈ Total ÷ 55 sq ft of usable slab, rounded up — a planning figure, since slab sizes and seam layouts vary
Worked example
An L-shaped kitchen: 10 ft + 6 ft of counter at standard depth.
- Runs = (120 + 72) in × 25.5 in = 4,896 sq in = 34.0 sq ft
- 4 in backsplash = 192 in × 4 in = 768 sq in = 5.3 sq ft
- Total = 39.3 sq ft — one standard slab covers it at the 55 sq ft planning figure
- At an installed $65 per sq ft, expect quotes around $2,555 before edge upgrades and cutout fees
Assumptions and limitations
- Depths are uniform across runs. Waterfall ends, breakfast-bar overhangs wider than standard, and bump-outs should be measured as extra runs at their own depth.
- The 55 sq ft usable-per-slab figure is a planning average for common slab sizes after seams and defects. Exotic materials sold in smaller slabs, and kitchens needing long seam-free runs, use more slabs — your fabricator's layout is final.
- Edge profiles, cutout polishing and sink mounting are usually per-piece fees on top of the per-sq-ft rate; the cost line here multiplies area only.
- For an L-shape, measure each leg wall-to-wall and let the corner overlap once — the standard method double-counts nothing if each leg is measured to the wall and the depth is uniform.
Frequently asked questions
For each run, multiply length by depth in inches and divide by 144. A 10 ft (120 in) run at the standard 25.5 in depth is 21.25 sq ft. Add every run, the island, and the backsplash strip (total run length × splash height ÷ 144). The calculator does the sum and shows each piece.
25.5 in for kitchens: 24 in base cabinets plus a 1.5 in front overhang. Bathroom vanities are usually 22 in deep. Islands vary — 36–42 in is typical when there is seating on one side.
Many do — the slab material was consumed and the cutout itself is billable work (cutting and polishing the edge). Others deduct the area and charge a cutout fee instead. The calculator's toggle shows your area both ways so you can match whichever basis a quote uses.
Usually one. A standard slab yields roughly 55 sq ft of usable counter after seams and trimming, so kitchens up to about 50 sq ft are typically one-slab jobs — which is why staying under that line saves real money. Vein-matched layouts are the exception: matching the pattern across seams can push a 40 sq ft kitchen to two slabs.
It roughly adds the equivalent of a second counter run in area terms (18 in of splash versus 25.5 in of counter). It looks premium and eliminates a grout line behind the range, but it is the single biggest area adder in most quotes — the height selector lets you price all three options before committing.