How this calculator works
The area of a run of counter is its length along the wall times its depth. When two runs meet in a corner, the square where they overlap is counted once, so the second run is shortened by the depth. An island is its length times its width, and a backsplash is the length of wall times its height. The slabs to order are the total area plus an allowance for cuts, seams and unusable edges, divided by the area of one slab, rounded up.
Worked example: an L-shaped kitchen with runs of 12 ft and 8 ft, 25½ in deep, has 38.0 ft² of counter (a single 12 ft run would be 25.5 ft²). With a 6 × 3 ft island (18 ft²) and a 4 inch backsplash (6.7 ft²) the total is 62.7 ft², and with a 20% allowance 75.2 ft², which is 2 quartz slabs of 55 ft² (2 granite slabs of 46 ft²). A full-height 18 inch backsplash brings the total to 86.0 ft².
Countertop area for common kitchens (25½ in deep, no island or backsplash)
Straight, L-shaped and U-shaped runs.
| Layout | Area | With 20% allowance | Quartz slabs |
|---|---|---|---|
| 8 ft | 17.0 ft² | 20.4 ft² | 1 |
| 12 ft | 25.5 ft² | 30.6 ft² | 1 |
| 10 + 6 ft | 29.5 ft² | 35.4 ft² | 1 |
| 12 + 8 ft | 38.0 ft² | 45.6 ft² | 1 |
| 12 + 8 + 6 ft | 46.2 ft² | 55.5 ft² | 2 |
| 16 + 10 + 8 ft | 63.2 ft² | 75.9 ft² | 2 |
Tips before you buy
- Measure the length along the wall for each run, and the depth from the wall to the front edge. Add 1 to 1½ inches of overhang over the cabinets.
- Corners are counted once: where two runs meet, the corner square belongs to only one of them.
- Stone counters are cut from a slab, so the cost depends on the slab count rather than the exact area. A layout that fits two runs on one slab can save a lot.
- Look at the slab in person before you buy, since veining and color change from slab to slab.
- Ask the fabricator about edges, cutouts, a sink style (undermount needs stone support) and the cost of seams.
Tools & materials for this project
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Frequently asked questions
How many square feet is a kitchen countertop?
An L-shaped kitchen with runs of 12 and 8 feet, 25½ inches deep, has about 38 ft² of counter; with a 6 × 3 ft island and a 4 inch backsplash the total is 63 ft².
How do you calculate countertop square footage?
Multiply each run's length by its depth in feet (25½ inches is 2.125 ft), take the corner overlap off the second run, and add the island and the backsplash. A 12 ft run is 25.5 ft².
How many slabs do I need for my countertops?
About 2 quartz slabs for the 63 ft² kitchen, with a 20% allowance. The fabricator's layout decides the real number.
How much does a granite countertop weigh?
About 16 to 17 pounds per square foot for 3 cm stone, so 1,034 pounds for this kitchen. Standard base cabinets carry that, with a sink and cooktop supported properly.
What is the standard countertop depth?
Base cabinets are 24 inches deep, and counters are normally 25 to 25½ inches deep with a 1 to 1½ inch overhang at the front.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.