Countertop Calculator

To calculate countertop material, multiply each section's length by its depth, add the runs together, add any backsplash area, subtract sink or cooktop cutouts, then add a waste allowance. In one formula: total = ((length x depth x sections) + (backsplash length x backsplash height) - cutouts) x (1 + waste / 100).

Every field above maps to one term. Length is the longest straight run of each counter. Depth is the front-to-wall distance, and the standard finished depth is 25.5 inches, which covers 24 inches of cabinet plus the overhang. Backsplash counts only when it uses the same stone or laminate. Divide by 144 when your measurements are in inches to convert square inches to square feet.

Here is the full arithmetic for one straight kitchen run, step by step. Take a 10 ft counter that is 2 ft deep: 10 x 2 = 20 sq ft of counter. Add a matching backsplash 10 ft long and 1.5 ft high: 10 x 1.5 = 15 sq ft. Net is 20 + 15 = 35 sq ft. With a 10% waste allowance: 35 x 1.10 = 38.5 sq ft to buy.

Divide by the usable slab yield of 50 sq ft: 38.5 / 50 = 0.77, so you buy 1 slab. The leftover slab stock covers cutting waste and future repairs. Without the backsplash the same counter is 20 sq ft net, 22 sq ft with 10% waste, still 1 slab. The same area logic applies to other projects: the tile calculator turns floor and wall square footage into tiles and boxes.

Break an L-shape or U-shape into straight rectangles and measure each one wall to wall. A 12 ft run meeting an 8 ft run, both 25.5 inches deep, becomes two sections: 12 x 2.125 = 25.5 sq ft and 8 x 2.125 = 17 sq ft, for 42.5 sq ft net before waste. Use the number of sections field for identical runs, or run the calculator once per different-depth section and add the results.

The corner where the two runs meet gets counted twice if you measure both runs wall to wall. That double-counted corner is about 4.5 sq ft at standard depth, and most fabricators treat it as part of the cutting waste rather than something you must subtract. It also feeds other material estimates: the flooring calculator turns the same room dimensions into planks or tiles.

Ten percent is the standard waste allowance for a straight run with few cutouts: it covers edge trimming, the sink and cooktop cutouts, and one miscut. Raise it to 15 percent for L-shapes, and to 15 to 20 percent for U-shapes, diagonal cuts, or pattern-matched stone where offcuts cannot be reused.

Set waste to zero only when you already know the exact finished yield from your fabricator, for example when they quote you in net square feet plus a fixed overage. Otherwise the waste allowance is what keeps a 20 sq ft counter from leaving you 2 sq ft short after the sink cutout.

A standard granite or quartz slab measures about 9 to 10 ft long and 5 to 6 ft wide, roughly 45 to 60 sq ft gross. After the fabricator trims the irregular edges, the usable yield is about 50 sq ft per slab. Divide your total square footage with waste by 50 and round up: 38.5 sq ft means 1 slab, 62 sq ft means 2 slabs.

Always round up to a whole slab, because slabs are sold whole and the leftover is useful. Keep the remnant for repairs or a matching vanity top; the concrete calculator works the same way for cast-in-place concrete counters, rounding up to whole bags and yards.