About the Countertop Calculator
This countertop calculator adds up the square footage of kitchen or bathroom countertops so you can compare quotes for granite, quartz, marble, butcher block or laminate. Enter up to three straight runs (enough for straight, L-shaped and U-shaped layouts), an optional island or peninsula, and a backsplash height, and it totals the area, adds a fabrication waste allowance and estimates the cost including sink and cooktop cutout fees.
To avoid double-counting corners on an L or U shape, measure the first run along the full back wall, then measure the next run from the front edge of the first counter to its end. Depth is usually 25½ in for base cabinets (24 in cabinets plus a 1½ in overhang); islands are often 36–42 in deep.
Stone fabricators price by the square foot of finished countertop or by the slab, and most charge extra for cutouts, edge profiles and installation. The default $60 per sq ft installed price is only a placeholder — granite, quartz, marble and laminate prices vary several-fold by material grade and region — so replace it with a local quote. The slab count in the notes assumes about 50 sq ft of usable stone per slab (slabs typically yield roughly 45–55 sq ft); ask your fabricator for their actual slab size. Treat the result as a budgeting estimate and confirm with a template-based quote.
With the default inputs, the total area (tops + backsplash) is 53.13 sq ft. Change any value above to recalculate instantly.
How to use the countertop calculator
- 1Measure the first countertop run along the full wall, including the corner.
- 2Measure other runs from the front edge of the first run so corners are not counted twice.
- 3Add any island or peninsula and the backsplash height.
- 4Enter your price per square foot, waste allowance and number of cutouts.
- 5Compare the estimated cost with fabricator quotes.
Formula and method
Each straight section of countertop is a rectangle, so its area is length times depth. Measuring in inches and dividing by 144 converts square inches to square feet. An L or U shape is split into rectangles; measuring each later run from the front edge of the previous one keeps the corner square from being counted twice.
A backsplash runs along the wall-side runs (not the island), so its area is the wall length behind those runs times the backsplash height. Because runs 2 and 3 are measured from the front edge of run 1, the wall behind each of them is longer by run 1’s depth, and that is added back. A waste allowance covers seams, overhangs and slab offcuts, and fixed cutout fees for sinks and cooktops are added to the per-square-foot cost.
- Length, Depth
- Dimensions of each countertop section (in)
- Waste%
- Fabrication allowance for seams and offcuts
- Price
- Cost per square foot (installed)
Worked examples
L-shaped kitchen with island
Run 1 is 96 × 25.5 = 2,448 in², run 2 is 72 × 25.5 = 1,836 in² and the island 72 × 36 = 2,592 in², totalling 47.75 sq ft. The backsplash runs along 96 in of wall plus 72 + 25.5 = 97.5 in behind run 2 (the corner depth is wall too), so a 4 in splash adds 193.5 × 4 ÷ 144 = 5.375 sq ft. That is 53.13 sq ft; with 10% waste at $60 plus one $150 cutout, the estimate is about $3,656.
10 ft straight run, no backsplash
120 × 25.5 = 3,060 in², or 21.25 sq ft. Adding 10% waste gives 23.38 sq ft, which at $45 per sq ft plus one $150 sink cutout comes to about $1,202.
Frequently asked questions
How do I measure countertops for square footage?+
Split the countertop into rectangles, multiply each length by its depth in inches, add them up and divide by 144. For L-shapes, measure the second leg from the front edge of the first so the corner is counted once.
What is the standard countertop depth?+
Kitchen base cabinets are 24 in deep and countertops typically overhang by about 1½ in, giving a 25½ in depth. Bathroom vanity tops are commonly 22 in deep.
How much do granite or quartz countertops cost per square foot?+
Installed prices vary widely by region, stone grade, edge profile and fabricator. Get local quotes and enter your price per square foot here to budget the full job.
Is the backsplash included in countertop square footage?+
Fabricators usually price a stone backsplash by the square foot like the countertop, so it is added here. A tile backsplash is priced separately and you can set the backsplash height to 0.
Why add waste to a countertop estimate?+
Stone is cut from slabs of fixed size, so seams, overhangs and grain matching leave offcuts. A 10–15% allowance approximates the extra material you pay for.