How to use the countertop calculator
Stone, quartz and solid-surface countertops are priced by area, but they are cut from slabs of a fixed size, and the edges and backsplash add to the bill. This calculator adds up your runs, island and backsplash, converts them into square feet or square metres, estimates how many slabs a fabricator will need and gives the length of finished edge to price a profile.
- Choose units. US mode takes inches, the way kitchen plans are dimensioned, and reports square feet. Metric mode takes millimetres and reports square metres.
- Enter the depth and up to three runs. For an L or U shape, measure the first run into the corner and each following run from the front edge of the one before, so corners are only counted once.
- Add the island and the backsplash height if it is in the same material, plus any run ends that are exposed rather than against a wall or appliance.
- Check the slab size for your chosen material and set a yield. Add an installed price per area for a budget figure.
Countertop formulas
Run area = Σ run length × depth · Island area = island length × island depth
Backsplash area = Σ run length × backsplash height
Total area = run area + island area + backsplash area (÷ 144 for ft² from in²)
Slabs = ⌈total area ÷ (slab length × slab width × yield %)⌉
Finished edge = Σ run lengths + exposed ends × depth + island perimeter
The slab count is an area estimate. The real count depends on how the pieces nest on the slab, so the calculator also flags any piece that is longer or deeper than the slab and therefore needs a seam. The backsplash length follows the runs; it does not include the island, or returns at the ends of a run.
| Item | US typical | Metric typical |
|---|---|---|
| Kitchen counter depth | 25–25.5 in | 600–650 mm |
| Bathroom vanity depth | 19–22 in | 450–550 mm |
| Island depth | 36–48 in | 900–1,200 mm |
| Standard quartz slab | ≈ 120 × 55 in | ≈ 3,000 × 1,400 mm |
| Jumbo quartz slab | ≈ 130 × 65 in | ≈ 3,200 × 1,600 mm |
| Upstand / full backsplash | 4 in / 18 in | 100 mm / 450–500 mm |
Worked examples
An L-shaped kitchen with an island
Two runs of 120 in and 96 in at 25.5 in deep cover 3,060 and 2,448 in², or 21.25 and 17 ft². A 72 × 36 in island adds 18 ft², so the counters total 56.25 ft². A 4 in backsplash along both runs adds 864 in², or 6 ft², giving 62.25 ft². A standard 120 × 55 in slab is 45.8 ft², or 36.7 ft² usable at 80%, so the job needs two slabs. The finished edge is the 216 in of run fronts, one 25.5 in exposed end and the island's 216 in perimeter: about 38.1 ft. At $75 per square foot installed, that is roughly $4,670.
A galley run and island in millimetres
A 3,000 × 600 mm run is 1.8 m², and a 2,400 × 900 mm island is 2.16 m². A 100 mm upstand along the run adds 0.3 m², so the total is 4.26 m². A 3,000 × 1,400 mm slab gives 4.2 m², or 3.36 m² usable at 80%, so the estimate is two slabs; the 600 mm and 900 mm pieces together are also deeper than one 1,400 mm slab. The finished edge is 3.0 m plus the island's 6.6 m perimeter, 9.6 m in total.
Who this calculator helps
- Kitchen and bath designers checking a layout against slab sizes before sending it to a fabricator.
- Interior designers and architects budgeting worktops in a finishes schedule or cost plan.
- Fabricators and installers turning a customer's sketch into a quick quote.
- Homeowners comparing quartz, granite and laminate prices per square foot on the same kitchen.
Practical tips
- Plan seams over a cabinet centre line, away from the sink and cooktop, and ask to see the slab layout before cutting.
- Check the working space between counters and the island with the kitchen work triangle checker and the furniture clearance guide.
- For a tiled backsplash instead of stone, take the wall area to the tile calculator.
- Templating after the base cabinets are fixed gives the most accurate final measurements.
Want to compare white quartz with dark granite before choosing? Show the client the finished kitchen on a photo with Room Redesign.
