Countertop Slab Size Calculator

Understanding Countertop Slab Sizing

Natural stone and engineered quartz countertops are sold as full slabs that are then cut to fit your specific layout. Slab sizes vary by material type and quarry, but most fall within standard ranges. Understanding slab dimensions helps you determine how many slabs you need, whether your countertop can be cut from a single piece (avoiding visible seams), and how to budget for your project accurately.

Standard Slab Sizes by Material:

Every square metre figure in that table is the square foot figure converted, so quartz and quartzite read the same 4.26 despite having differently shaped slabs. They cover the same 6,600 square inches, one long and narrow, the other shorter and deeper. Which shape suits you depends on your longest run: a 120-inch quartz slab covers a 10-foot counter in one piece where a 110-inch quartzite slab does not.

Calculating Your Countertop Area:

Countertops are not simple rectangles. A typical kitchen has L-shaped or U-shaped counters with cutouts for sinks and cooktops. To calculate the total countertop area, break your layout into rectangular sections and add them together.

Total Area = Section 1 (Length x Width) + Section 2 (Length x Width) + ...

Standard countertop depth is 25.5 inches (65 cm) for kitchen cabinets and 22.5 inches (57 cm) for bathroom vanities. These include a 1.5-inch (3.8 cm) overhang past the cabinet face.

Waste and Seam Planning:

When cutting a countertop from a slab, there is always waste material. Straight cuts produce less waste (typically 10 to 15 percent), while complex shapes with curves and cutouts waste more (20 to 30 percent). Plan seam locations at natural break points like behind a sink or at an inside corner where they are less visible. Most fabricators prefer seams to fall at least 6 inches (15 cm) away from sink and cooktop cutouts to maintain structural integrity.

Weight Considerations:

Countertop weight matters for cabinet support and installation planning. A 3 cm (1.25 inch) thick granite slab weighs approximately 18 to 20 pounds per square foot (88 to 98 kg per square meter). A full slab weighs 700 to 900 pounds (318 to 408 kg). Quartz is slightly heavier at about 20 to 22 pounds per square foot (98 to 107 kg per square meter). Ensure your base cabinets can support this weight, especially for large island pieces.

Cost Estimation:

Material costs vary widely, and the figures below are approximate US market ranges as of 2026 rather than a quote. Budget granite starts around 40 per square foot installed, mid-range quartz runs 60 to 100, and premium marble can exceed 150. Fabrication and installation typically add 30 to 50 per square foot on top of the material cost.

Always get material and fabrication as separate line items, because they are charged on different quantities. Material is sold by the slab, so you pay for the whole slab even if your layout uses two thirds of it. Fabrication is charged on the finished square footage you actually end up with. A quote that gives you one blended number per square foot is hiding which of the two is high.