How much countertop do I need?
Type the length and depth of each counter run, the backsplash height, and your slab size. The countertop calculator shows the square feet to order, the slabs by area, and the cost at your price.
- Square feet to order
- 43.3
Order 43.3 ft² of countertop; slabs by area: 1.
- Counter area
- 34
- Backsplash area
- 5.3
- Square meters to order
- 4.02
- Slabs (by area)
- 1
Square feet to order: 43.3. Order 43.3 ft² of countertop; slabs by area: 1.
How to calculate
Computes the square feet of countertop for up to three runs, plus backsplash and extra for cuts, how many slabs that is by area, and the cost at a price per square foot.
Example with the default inputs (Counter runs 2, Run 1 length 120 in, Run 1 depth 25.5 in, Run 2 length 72 in, Run 2 depth 25.5 in, Backsplash height 4 in, Extra for cuts 10%, Slab length 120 in, Slab width 60 in): Order 43.3 ft² of countertop; slabs by area: 1.
Method: Counter area = Σ length × depth; backsplash = Σ length × backsplash height; to order = (counter + backsplash) × (1 + extra ÷ 100); slabs = to order ÷ (slab length × slab width), rounded up; cost = to order (ft²) × price.
- Each run is a rectangle; measure an L or U as separate runs that do not overlap.
- The backsplash runs along the full length of every run, in the same material.
- Slabs by area is the least that could work; seams, grain and cutouts often need one more.
Worked examples
Each example is checked against the calculator on every build.
- Counter runs 2, Run 1 length 120 in, Run 1 depth 25.5 in, Run 2 length 72 in, Run 2 depth 25.5 in, Backsplash height 4 in, Extra for cuts 10%, Slab length 120 in, Slab width 60 in, Price per square foot $60.00 gives Counter area 34, Backsplash area 5.333333, Square feet to order 43.266667, Slabs (by area) 1, Cost $2,596.00.Source: NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 ft² = 144 in² = 0.09290304 m², https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18); OpenStax, Prealgebra 2e, §9.4 (area of a rectangle = length × width), https://openstax.org/books/prealgebra-2e/pages/9-4-use-properties-of-rectangles-triangles-and-trapezoids (retrieved 2026-10-18)
- Counter runs 1, Run 1 length 96 in, Run 1 depth 36 in, Backsplash height 0 in, Extra for cuts 0%, Slab length 120 in, Slab width 60 in gives Counter area 24, Backsplash area 0, Square feet to order 24, Slabs (by area) 1, Square meters to order 2.229673.Source: NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 ft² = 144 in² = 0.09290304 m², https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18)
- Counter runs 3, Run 1 length 118.1 in, Run 1 depth 23.62 in, Run 2 length 78.74 in, Run 2 depth 23.62 in, Run 3 length 59.06 in, Run 3 depth 23.62 in, Backsplash height 3.937 in, Extra for cuts 15%, Slab length 118.1 in, Slab width 55.12 in gives Square meters to order 5.2325, Slabs (by area) 2.
How it works
Only the runs you count (1, 2 or 3) are used.
- Counter area = Σ length × depth, over the runs
- Backsplash area = Σ length × backsplash height, over the runs
- Area to order = (counter area + backsplash area) × (1 + extra ÷ 100)
- Slabs (by area) = area to order ÷ (slab length × slab width), rounded up to a whole slab
- Cost (only when you type a price) = area to order in ft² × price per ft²
Areas show in ft² (in² ÷ 144) and the area to order also in m² (1 ft² = 0.09290304 m² exactly).
Exact arithmetic. Each value is read as the exact decimal you typed, in its unit, so every step is exact; slabs are rounded up from the exact value.
Rounding. Square feet show with at most 1 decimal and square meters with at most 2, each rounded half up, trailing zeros left off. Money always shows to the cent, rounded half up ($2,596.00).
Assumptions
- Each run is a rectangle, and the runs do not overlap.
- The backsplash is the same material and runs along the full length of every run.
- The extra for cuts is 10% by default, from 0% to 100%.
- Lengths, depths and slab sides are 1 mm to 100 m; the backsplash is 0 to 100 m; the price is 0 to $100,000.
Worked examples by hand
An L-shaped kitchen: runs of 120 in and 72 in, 25.5 in deep, 4 in backsplash, 10% extra, 120 × 60 in slabs, $60 per ft². Counter: (120 + 72) × 25.5 = 4,896 in² = 34 ft². Backsplash: 192 × 4 = 768 in² = 5.33 ft². To order: 39.33 × 1.1 = 43.27 ft². A slab is 7,200 in² = 50 ft², so 1 slab by area. Cost: 43.2667 ft² × $60 = $2,596.00.
An 8 × 3 ft island, no backsplash, no extra. 8 × 3 = 24 ft² = 24 × 0.09290304 = 2.23 m², 1 slab.
A metric U-shape: runs of 3 m, 2 m and 1.5 m, 60 cm deep, 10 cm backsplash, 15% extra, 3 × 1.4 m slabs. Counter: 6.5 × 0.6 = 3.9 m²; backsplash 6.5 × 0.1 = 0.65 m²; to order (3.9 + 0.65) × 1.15 = 5.23 m². A slab is 4.2 m², so 2 slabs.
Other questions people ask
How do I calculate countertop square footage?
Multiply each run’s length by its depth in inches, add the runs up, and divide by 144. A 120 in run and a 72 in run, both 25.5 in deep, are (120 + 72) × 25.5 = 4,896 in², which is 34 ft².
How do I measure an L-shaped or U-shaped counter?
Split it into rectangles that do not overlap. Measure the first run wall to end, then measure the second run from the front edge of the first run to its end, so the corner square is counted once.
How do I add a backsplash?
Multiply the length of each run by the backsplash height. A 4 in backsplash along 192 in of counter is 192 × 4 = 768 in², or 5.33 ft². Set the height to 0 if the backsplash is tile or another material.
How many slabs of granite or quartz do I need?
Divide the area to order by one slab’s area and round up. That is the least that could work: seams, matching veins and cutouts often need one more slab, so ask your fabricator to lay out the pieces.
How much extra should I add?
About 10% covers sink and cooktop cutouts, seams and edge trimming. Sinks and cooktops are cut from the slab, so do not subtract them from the area you order.
How much does a countertop cost?
Multiply the square feet to order by the installed price per square foot from your quote. At $60 per ft², 43.27 ft² costs about $2,596. Prices vary with the stone, edge profile and region.