Pick the shape of your counter and measure each wall. You get the square feet a fabricator prices, the counters, island and backsplash on their own, and how many slabs each maker's own size takes, laid out to scale.
Your countertop
62.7 sq ft of countertoporder 63 sq ft · counters 38, island 18, backsplash 6.7 sq ft · 2 Caesarstone standard slabs (120 × 56.5″) · a seam in wall 1, a seam in backsplash 1
Quick answer: countertop square footage is each straight piece’s length × depth, added up and divided by 144 (inches to square feet), the way Caesarstone measures — round up. A standard kitchen counter is 25.5″ deep: a 12′ wall is 25.5 sq ft. A standard quartz slab is 120 × 56.5″ (Caesarstone) or 122 × 55.5″ (Cambria); a jumbo is up to 132 × 65.5″.
How to use the countertop calculator
- Pick the shape: straight, L, U or galley (two counters facing each other).
- Measure each wall’s counter from the corner to its end, front edge included, and its depth. Add the island’s length and depth, waterfall sides if it has them, and the backsplash’s height (0 for none).
- You get the square feet a fabricator prices — the counters, the island and the backsplash on their own — and how many slabs each maker’s own size takes, with your pieces laid out on the slab you pick and the seams named.
The rule behind the numbers
Caesarstone’s method: split the counter into rectangles, “ensuring your measurement for one segment does not overlap with the measurement for the next”, multiply each one’s length by its width, add them up and divide by 144. “Always round up.” Suppliers quote countertops by the square foot.
In an L or a U, the corner is where people count twice. Measure each wall from the corner and the calculator gives the corner square to one wall: in an L, wall 1 is its full length and wall 2 starts where wall 1’s counter ends, 25.5″ out; in a U, the middle wall takes both corners.
The depths: a kitchen counter is 25.5″ — a 24″ base cabinet and a 1.5″ overhang (Caesarstone). An island is often 27–28″ deep, and at least 30″ with seats. A backsplash rises three to six inches, “with four inches being the most common” (MSI). A waterfall side adds the island’s depth × the 36″ finished counter height, per side (Caesarstone).
Each maker’s slab size
| Maker | Slab | Size | Square feet |
|---|---|---|---|
| Caesarstone | Standard | 120 × 56.5″ | 47.1 |
| Caesarstone | Jumbo | 124.5 × 61.5″ ± 1% | 53.2 |
| Caesarstone | Jumbo | 131.5 × 64.5″ | 58.9 |
| Cambria | Standard | 122 × 55.5″ | 47 |
| Cambria | Jumbo | 132 × 65.5″ | 60 |
| Silestone | Standard | 3060 × 1400 mm | 46.1 |
| Silestone | Jumbo | 3250 × 1590 mm | 55.6 |
Each size is the maker’s own: Caesarstone’s US countertop page, Cambria’s Designs Product Guide (effective August 26, 2026; it calls the slabs 47 and 60 square feet), and Cosentino’s Silestone listing, in millimetres. Not every color comes in every size. Cambria adds: check with your fabricator for the largest piece it can cut from a slab, as against the size listed.
Five worked examples
An L with a 12′ and an 8′ wall, a 6 × 3′ island and a 4″ backsplash. The counters come to 38 sq ft, the island 18, the backsplash 6.7: 62.7 sq ft — order 63. That is 2 slabs of any maker’s size, and the 12′ wall needs a seam on all of them.
One 10′ counter with a 4″ backsplash. 24.6 sq ft, and it fits on 1 slab of every size in the table.
A U with walls of 10′, 12′ and 8′. 64.7 sq ft with the backsplash. The 12′ middle wall is longer than every slab, even a 132″ jumbo, so it has a seam whichever you pick.
An 8′ × 42″ island with two waterfall sides. The top is 28 sq ft and the sides add 21 sq ft more: 49 sq ft for the island alone.
A 10½′ island, 42″ deep. No standard slab is 126″ long, and neither is Caesarstone’s 124.5″ jumbo: the island has a seam. Caesarstone’s 131.5″, Cambria’s 132″ and Silestone’s 3250 mm jumbos take it in one piece.
Common mistakes
- Counting the corner twice. Two walls measured from the corner overlap by a 25.5″ square — about 4.5 sq ft in every L.
- Measuring the cabinet, not the counter. The counter is 1.5″ deeper than a 24″ base cabinet, and an island with seats is 30″ or more.
- Forgetting the backsplash and waterfall sides. A 4″ backsplash on 20′ of wall is 6.7 sq ft; a waterfall side on a 42″ island is 10.5 sq ft.
- Ordering square feet, not slabs. Slabs come whole: 62.7 sq ft fits in 2 standard slabs only if the pieces lay out that way.
- Not asking about seams. A piece longer than the slab is cut in two; a jumbo can save the seam on a 10½–11′ island.
Size the island and its seating with the kitchen island size calculator, the cabinets with the kitchen cabinet height calculator, and the backsplash tile with the tile calculator. Draw the kitchen to scale in the free 2D planner.
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Countertop size questions
How do you calculate countertop square footage?
Split the counter into rectangles that do not overlap, multiply each one’s length by its depth in inches, add them up and divide by 144. A 12′ counter 25.5″ deep is 144 × 25.5 ÷ 144 = 25.5 sq ft. Round up.
What is the standard countertop depth?
25.5″ for a kitchen counter: a 24″ base cabinet and a 1.5″ overhang (Caesarstone). An island is often 27–28″ deep, and at least 30″ with seating.
What size is a quartz slab?
A standard slab is 120 × 56.5″ from Caesarstone, 122 × 55.5″ from Cambria and 3060 × 1400 mm (about 120.5 × 55″) from Silestone — about 46–47 sq ft.
What is a jumbo quartz slab size?
Caesarstone’s jumbos are 124.5 × 61.5″ (± 1%) and 131.5 × 64.5″; Cambria’s is 132 × 65.5″, about 60 sq ft; Silestone’s is 3250 × 1590 mm (about 128 × 62.6″).
What size is a Cambria slab?
Cambria’s Designs Product Guide: a standard slab is 122 × 55.5″ (47 sq ft), a jumbo 132 × 65.5″ (60 sq ft), and a half slab 132 × 32.75″.
How many slabs of quartz do I need?
Lay your pieces out on the slab’s size: an L of 12′ and 8′ with a 6′ island takes 2 standard slabs. A piece longer than the slab — a 12′ wall on a 120″ slab — is cut in two, with a seam.
How much do quartz countertops cost?
Caesarstone puts material and installation at “typically $40 to more than $100 per square foot”: a 62.7 sq ft kitchen is about $2,500–$6,300 or more.
How do you calculate backsplash square footage?
The length of wall it runs along × its height, ÷ 144. A 4″ backsplash on 20′ (240″) of wall is 240 × 4 ÷ 144 = 6.7 sq ft.