How do you calculate countertop square footage?

Split the counters into rectangles, multiply each length by its depth in inches and divide by 144, then add them up. The example kitchen is 12 ft × 25.5 in = 25.5 sq ft, 8 ft × 25.5 in = 17, 3 ft × 25.5 in = 6.38 and a 6 ft × 42 in island = 21, which is 69.88 sq ft. Add the backsplash and you have the number a fabricator quotes.

What is the standard countertop depth?

Base cabinets are 24 in deep and the countertop overhangs the doors by about 1.5 in, so the usual depth is 25.5 in. Bath vanities are often 21 to 22 in deep. Measure your own: an older kitchen or an overhang of 1 in or 2 in changes the depth, and every inch of depth on a 12 ft run is a full square foot.

How much overhang does an island need?

For seating, 12 in is the least that works and 15 in is more comfortable; 15 in is the figure often attributed to the NKBA for counter-height stools, though sources differ and the NKBA’s own wording was not checked. Past about 12 in the stone needs support, such as corbels or steel brackets. Put the whole width in the island width field: a 24 in cabinet, 1.5 in overhang on the work side and 12 to 15 in on the seating side is about 40 in. At 48 in wide the island in the example is 24 sq ft instead of 21.

Do fabricators deduct the sink and cooktop cutouts?

Usually not. Most fabricators quote the full rectangle and charge separately for the cutout itself, because the stone still has to be bought and cut and the cutout piece is scrap or goes back to the customer. Not all shops agree, and some deduct a standard sink opening or a cutout over a certain size, so ask for the shop’s rule before comparing bids. This calculator deducts nothing by default; "Subtract an area" is there for a shop that does.

How many square feet is a backsplash?

Length × height ÷ 144 with the height in inches. A 4 in splash along 20 ft is 6.67 sq ft. A full-height backsplash is much more: the same 20 ft at 18 in is 30 sq ft. Many stone backsplashes are 4 in, and a tiled backsplash is measured separately, with the backsplash calculator.

How many slabs do I need for my countertops?

Divide the total sq ft with waste by the area of one slab and round up. The example needs 84.2 sq ft, and a 130 × 65 in jumbo quartz slab is 58.68 sq ft, so 2 slabs. On a standard 120 × 56 in slab (46.67 sq ft) with 15% extra it is 2. This is an estimate: only the layout on the actual slabs can say, because pieces must fit the slab’s width, veining may fix the direction, and seams are placed by the fabricator.

What size is a quartz or granite slab?

A standard quartz slab is roughly 120 × 56 in, and jumbo slabs run from about 125 × 62 to 131 × 65 in (Caesarstone lists 131.5 × 64.5 in; MSI quotes 126 × 64 or 130 × 65 in; Silestone jumbo is listed at 128 or 129 × 63 in). Granite slabs vary by stone and quarry; 110 × 60 in is only a typical figure. Check the actual slab with the yard or your fabricator. Sizes change with the maker and the color.

How much waste should I allow for countertops?

About 10% for a few simple runs, about 15% for an L or U shape with seams, and 20% or more for veined or patterned stone that is matched across seams, or when the pieces are awkward to nest. Fabricators often take the slab, not the square foot, as their cost, so what you pay for is the whole slab you cut from. These are rules of thumb and not a standard.

How much does countertop cost per square foot?

It depends on the material, edge, region and the cutouts, so this calculator assumes no price. Enter the fabricator’s installed price per sq ft; at $75 per sq ft the example's 76.54 sq ft is $5,741. A quote prices the sq ft before waste, since the waste is built into the price per sq ft.

Countertop Square Footage Calculator

An L-shaped kitchen with a 12 ft run, an 8 ft run and a 3 ft run, all 25.5 in deep, plus a 6 ft island 42 in wide, is 69.88 sq ft of countertop. A 4 in backsplash along 20 ft adds 6.67 sq ft, so a fabricator would quote about 76.54 sq ft. With 10% for waste and seams that is 84.2 sq ft of stone, roughly 2 slabs of jumbo quartz, 130 × 65 in (58.68 sq ft each). The slab count is an estimate: the layout decides. Each piece is length × depth ÷ 144 (in inches), and sink and cooktop cutouts are normally not deducted.

Figures based on the sources listed belowUpdated 2026-10-11How we calculate

Run 1 length

Run 1 depth

Run 2 length

A second straight run, such as the other leg of an L. Count the corner once: run 1 to the wall, run 2 from the corner. Leave 0 for none.

Run 2 depth (in)

Base cabinets are 24 in deep; with a 1.5 in front overhang the top is 25.5 in. A bath vanity is often 21 to 22 in.

Run 3 length

A third run for a U-shape, a peninsula or a bar (3 ft of it in the example). Leave 0 for none.

Run 3 depth (in)

Island length

The top of the island, end to end. Leave 0 for no island.

Island width (in)

The full width including overhangs. A 24 in cabinet with a 1.5 in overhang on the work side and a 12 to 15 in seating overhang on the other is about 40 in. Seating overhangs of 12 in and up usually need support brackets.

Backsplash length

The length of wall that gets a stone backsplash, along the runs. Leave 0 for none, or if you will tile it (see the backsplash calculator).

Backsplash height (in)

A 4 in splash is the usual stone one. A full-height stone backsplash runs up to the upper cabinets, 18 in or more.

Slab sizeTypical sizes only. Slab sizes vary by maker and color, and the usable area is a little less than the full slab. Ask your fabricator for the slab you are buying.

Installed price per sq ft in dollars (optional)

The fabricator’s quoted price per square foot, installed. Prices vary widely with material and region, so none is assumed. It prices the total sq ft before waste, as a quote does; the "Price per slab" box below prices whole slabs bought from a yard.

Price per slab (optional)

Buy 2 slabs

76.54 sq ft + 10% waste = 84.20 sq ft

Countertop (runs and island): 70 sq ft
Backsplash: 7 sq ft
Total to quote: 77 sq ft, before waste
Slabs (estimate: the layout decides): 2 slabs (each 59 sq ft)
Installed cost (estimate): Enter an installed price per sq ft to see a cost

How this number is calculated

76.54 sq ft + 10% waste = 84.20 sq ft ÷ 58.68 sq ft per slab = 2 slabs

Shopping list

Tape measure (25 ft)
Laser distance measurer
Silicone adhesive for stone
Stone countertop sealer
Granite cleaner

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Countertop sq ft by length and depth

One rectangle, length × depth ÷ 144 with the depth in inches, worked by this calculator with no waste. Add a run’s rectangles together; count an L’s corner once.
Depth	6 ft	8 ft	10 ft	12 ft	15 ft	20 ft
22 in (bath vanity)	11	14.67	18.33	22	27.5	36.67
25.5 in (base cabinets with overhang)	12.75	17	21.25	25.5	31.88	42.5
30 in (deeper counter)	15	20	25	30	37.5	50
42 in (island with seating)	21	28	35	42	52.5	70

Typical slab sizes

Nominal sizes from the sources below; real slabs vary by maker, color and thickness, and you can enter any area with Custom slab area. The granite size is an unverified typical figure.
Size	Material	Area (sq ft)
120 × 56 in	Quartz (standard)	46.67
126 × 64 in	Quartz (large)	56
130 × 65 in	Quartz (jumbo)	58.68
110 × 60 in	Granite (typical)	45.83

Slabs by total sq ft, slab size and waste

Total sq ft (counter plus backsplash) ÷ slab area with 10% or 20% waste, rounded up, worked by this calculator. An estimate: the layout decides, and a long or L-shaped run may need more.
Total	Standard quartz, 10%	Standard quartz, 20%	Jumbo quartz, 10%	Jumbo quartz, 20%
30 sq ft	1	1	1	1
40 sq ft	1	2	1	1
50 sq ft	2	2	1	2
60 sq ft	2	2	2	2
75 sq ft	2	2	2	2
100 sq ft	3	3	2	3

Methodology & assumptions

Every run is measured as a rectangle: length × depth, with the depth in inches ÷ 12 to get sq ft. Run 1 is the length and depth fields; runs 2 and 3, the island and the backsplash are the other fields. Add the rectangles for the countertop, add the backsplash (length × height), and that total is the square footage a fabricator quotes. For an L, measure one leg all the way to the wall and the other from the corner of the first, so the corner is counted once; for a U, the same with the third leg. Depth is the cabinet box plus the overhang: base cabinets are 24 in deep and the top overhangs the doors by about 1.5 in, so 25.5 in is the usual depth. A bath vanity is often 21 to 22 in deep, and an island with seating adds a 12 to 15 in overhang to the work side. Sink and cooktop cutouts are not deducted by default: most fabricators quote the full rectangle, because the cutout is scrap or a piece the shop keeps, and the stone still has to be bought and cut. Shops differ, so ask yours; if one deducts, use "Subtract an area" for the cutout. The waste or seam allowance (10% for simple runs, 15% for L or U shapes with seams, 20% for veined stone that is matched across seams) is added to the total, and the result is divided by the area of one slab and rounded up. That slab count is an estimate: it treats the slabs as one pool of area, but the layout decides: pieces must fit inside the slab's width, veining and pattern direction limit how they can be turned, edges of a slab are not usable, and a single long run may need a seam. A fabricator lays the pieces on the actual slabs, and sometimes slabs are sold as a pair or in a bundle. Cost is the installed price you enter per sq ft times the total sq ft before waste, the way a quote works; nothing is assumed, because prices vary widely with material, edge, region and the number of cutouts. The metric toggle shows lengths in m and depths in cm; areas show in m².

Caesarstone, product and countertop pages (caesarstoneus.com): standard slab about 120 × 56.5 in; jumbo about 124.5 × 61.5 in and 131.5 × 64.5 in; availability varies by color
MSI Surfaces, "Why Super Jumbo Slabs? A Deep Dive Into Rusta and Belaros Quartz" (December 2025): standard quartz slabs typically 126 × 64 in or 130 × 65 in
Cosentino Silestone slab listings (DesignShop, MaterialBank): jumbo slabs of 128 or 129 × 63 in; standard 120 × 56 in. Retailer listings, not Cosentino’s own spec sheet
Living Etc, "Kitchen countertop standard depth": a 24 in base cabinet with a 1.5 in overhang is the standard 25.5 in counter. A designer’s statement, not a code; the NKBA’s own wording was not checked
Slabwise countertop measuring guides (slabwise.com/guides): fabricators commonly quote the gross rectangle without deducting sink cutouts, with 10% extra for simple layouts and 15% for L or U shapes; shops differ, so ask yours. A trade blog, so the waste percentages are rules of thumb
Granite slab size (110 × 60 in): an unverified typical figure. Granite comes from the quarry in many sizes, so use Custom slab area with the slab you are shown

How to measure countertop square footage

Measure each run. Measure the length of each straight run to the wall, and count the corner of an L or U once, from the end of the run it meets.
Measure the depth. Use the cabinet depth plus the overhang: 25.5 in for standard base cabinets, 21 to 22 in for a vanity. Measure an island across, including the seating overhang.
Add the backsplash. Add the backsplash length and height if it is stone. 4 in is the usual height.
Do not deduct cutouts. Leave the sink and cooktop cutouts in the total, as most fabricators do, and ask your shop how it quotes them.
Add waste and pick a slab. Add 10 to 20% for waste and seams, pick the slab size and divide, rounding up. Treat the slab count as an estimate until the fabricator lays out the pieces.

Worked examples

Project	Result
L-shaped kitchen (12, 8 and 3 ft runs), 6 ft × 42 in island, 4 in backsplash along 20 ft, jumbo quartz, 10%	76.54 sq ft + 10% → 2 slabs (130 × 65 in), countertop 69.88 sq ft, backsplash 6.67 sq ft
The same kitchen without the island and the third run, 4 in backsplash along 10 ft	45.83 sq ft + 10% → 1 slabs (130 × 65 in), countertop 42.5 sq ft, backsplash 3.33 sq ft
Bath vanity: 5 ft × 22 in top with a 4 in backsplash along the 5 ft wall	10.83 sq ft + 10% → 1 slab (130 × 65 in), countertop 9.17 sq ft, backsplash 1.67 sq ft
The example kitchen on standard 120 × 56 in quartz slabs with 15% for seams	76.54 sq ft + 15% → 2 slabs (120 × 56 in)
The example kitchen on a 45 sq ft custom slab, 10%	76.54 sq ft + 10% → 2 slabs (45 sq ft each)

Frequently asked questions

How do you calculate countertop square footage?: Split the counters into rectangles, multiply each length by its depth in inches and divide by 144, then add them up. The example kitchen is 12 ft × 25.5 in = 25.5 sq ft, 8 ft × 25.5 in = 17, 3 ft × 25.5 in = 6.38 and a 6 ft × 42 in island = 21, which is 69.88 sq ft. Add the backsplash and you have the number a fabricator quotes.
What is the standard countertop depth?: Base cabinets are 24 in deep and the countertop overhangs the doors by about 1.5 in, so the usual depth is 25.5 in. Bath vanities are often 21 to 22 in deep. Measure your own: an older kitchen or an overhang of 1 in or 2 in changes the depth, and every inch of depth on a 12 ft run is a full square foot.
How much overhang does an island need?: For seating, 12 in is the least that works and 15 in is more comfortable; 15 in is the figure often attributed to the NKBA for counter-height stools, though sources differ and the NKBA’s own wording was not checked. Past about 12 in the stone needs support, such as corbels or steel brackets. Put the whole width in the island width field: a 24 in cabinet, 1.5 in overhang on the work side and 12 to 15 in on the seating side is about 40 in. At 48 in wide the island in the example is 24 sq ft instead of 21.
Do fabricators deduct the sink and cooktop cutouts?: Usually not. Most fabricators quote the full rectangle and charge separately for the cutout itself, because the stone still has to be bought and cut and the cutout piece is scrap or goes back to the customer. Not all shops agree, and some deduct a standard sink opening or a cutout over a certain size, so ask for the shop’s rule before comparing bids. This calculator deducts nothing by default; "Subtract an area" is there for a shop that does.
How many square feet is a backsplash?: Length × height ÷ 144 with the height in inches. A 4 in splash along 20 ft is 6.67 sq ft. A full-height backsplash is much more: the same 20 ft at 18 in is 30 sq ft. Many stone backsplashes are 4 in, and a tiled backsplash is measured separately, with the backsplash calculator.
How many slabs do I need for my countertops?: Divide the total sq ft with waste by the area of one slab and round up. The example needs 84.2 sq ft, and a 130 × 65 in jumbo quartz slab is 58.68 sq ft, so 2 slabs. On a standard 120 × 56 in slab (46.67 sq ft) with 15% extra it is 2. This is an estimate: only the layout on the actual slabs can say, because pieces must fit the slab’s width, veining may fix the direction, and seams are placed by the fabricator.
What size is a quartz or granite slab?: A standard quartz slab is roughly 120 × 56 in, and jumbo slabs run from about 125 × 62 to 131 × 65 in (Caesarstone lists 131.5 × 64.5 in; MSI quotes 126 × 64 or 130 × 65 in; Silestone jumbo is listed at 128 or 129 × 63 in). Granite slabs vary by stone and quarry; 110 × 60 in is only a typical figure. Check the actual slab with the yard or your fabricator. Sizes change with the maker and the color.
How much waste should I allow for countertops?: About 10% for a few simple runs, about 15% for an L or U shape with seams, and 20% or more for veined or patterned stone that is matched across seams, or when the pieces are awkward to nest. Fabricators often take the slab, not the square foot, as their cost, so what you pay for is the whole slab you cut from. These are rules of thumb and not a standard.
How much does countertop cost per square foot?: It depends on the material, edge, region and the cutouts, so this calculator assumes no price. Enter the fabricator’s installed price per sq ft; at $75 per sq ft the example's 76.54 sq ft is $5,741. A quote prices the sq ft before waste, since the waste is built into the price per sq ft.

Handy tools

Feet and Inches Calculator: Turn a tape reading like 9' 4 1/2" into the decimal feet the length fields take.