Countertop Calculator
Work out a countertop's net square footage after sink and cooktop cutouts, how many slabs or blanks it takes, and the material cost.
How countertop square footage is figured
Fabricators price stone and quartz by the square foot of finished counter, and the honest area is the gross run area minus the holes: a standard sink cutout is about 5 sq ft (a 33 × 22 in sink is a 5.04 sq ft hole) and a cooktop about 4.5 sq ft (30 × 21.5 in). Add your runs, take out the cutouts, and the net figure is both your price basis and the number that decides how many slabs the job eats.
Net area = (run lengths × depths) − 5 sq ft per sink − 4.5 sq ft per cooktop · Slabs = net area ÷ slab size, rounded up
Example: a 12 ft run and a 6 ft run, both 2 ft deep, make 36 sq ft gross. One sink comes out: 31 sq ft net — 1 granite slab covers it, and at $50 per square foot the material estimate is $1,550.
Slab sizes are the real constraint
| Material form | Typical size | Usable area |
|---|
| Granite slab | ~110 × 70 in | ≈ 110 sq ft class |
| Quartz slab, jumbo | 126 × 63 in | ≈ 55 sq ft |
| Quartz slab, standard | 120 × 55 in | ≈ 46 sq ft |
| Prefab blank | 25.5 × 96 in | 17 sq ft |
Standard counter depth is 25.5 in (about 65 cm) — an inch of overhang past a 24 in cabinet. Islands run deeper and are entered as their own run. The slab count here assumes a sane layout: a single unbroken run longer than the slab, or bold veining that must flow across an L, can force a second slab even when the area fits on one — that is a layout conversation with the fabricator, and worth having before the stone is cut, not after.
Frequently asked questions
Do fabricators charge for the cutout area?
Practices vary: many quote on the net finished area, some on the gross slab area used. The net figure from this calculator is the right basis for comparing quotes — ask each fabricator which basis their number sits on.
How much overhang does an island need for seating?
About 12 in (30 cm) of knee space for counter-height seating, 15 in for bar height. Add it to the island's depth when you enter the run — it is real counter area and real stone.
Can a remnant cover a small vanity?
Often, yes — fabricators keep slab remnants from larger jobs and sell them cheap for vanities and small counters. If your net area is small, ask about the remnant yard before pricing a whole blank.
Does the backsplash area count in the square footage?
Only if it is made of the same stone. A 4 in stone backsplash strip is usually priced as part of the job's linear work; a full-height stone backsplash is real area — measure it as another run (length × its height in feet) and add it.
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