# How much countertop do I need?

Computes the square feet of countertop for up to three runs, plus backsplash and extra for cuts, how many slabs that is by area, and the cost at a price per square foot.

- Page: https://www.acalculator.org/construction/countertop-calculator
- JSON spec: https://www.acalculator.org/construction/countertop-calculator.json
- Version: 2b0dce0d5ab4

## Default answer

Example with the default inputs (Counter runs 2, Run 1 length 120 in, Run 1 depth 25.5 in, Run 2 length 72 in, Run 2 depth 25.5 in, Backsplash height 4 in, Extra for cuts 10%, Slab length 120 in, Slab width 60 in): Order 43.3 ft² of countertop; slabs by area: 1.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| n | Counter runs | How many straight runs of counter: an L-shape is 2, a U-shape 3. Count an island as a run. |
| l1 | Run 1 length | The length of the first run along the wall. |
| d1 | Run 1 depth | The depth of the first run, front edge to wall (25.5 in is common). |
| l2 | Run 2 length | The length of the second run, not counting the part the first run covers. |
| d2 | Run 2 depth | The depth of the second run. |
| l3 | Run 3 length | The length of the third run. |
| d3 | Run 3 depth | The depth of the third run. |
| bs | Backsplash height | The height of a backsplash in the same stone along each run’s length; 0 for none. |
| extra | Extra for cuts | Material to add for sink and cooktop cutouts, seams and edge waste. |
| sl | Slab length | The length of one slab from your supplier. |
| sw | Slab width | The width of one slab. |
| price | Price per square foot | The installed price per square foot, from your quote. Leave empty to skip the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| total | Square feet to order | (Counter area + backsplash area) × (1 + extra ÷ 100), in ft². |
| counter | Counter area | The sum of length × depth over the runs, in ft². |
| backsplash | Backsplash area | The sum of the run lengths × backsplash height, in ft². |
| totalM2 | Square meters to order | The area to order, in m². |
| slabs | Slabs (by area) | Area to order ÷ one slab’s area, rounded up: the fewest slabs that could do it. |
| cost | Cost | Square feet to order × price per square foot. |

## Method

Counter area = Σ length × depth; backsplash = Σ length × backsplash height; to order = (counter + backsplash) × (1 + extra ÷ 100); slabs = to order ÷ (slab length × slab width), rounded up; cost = to order (ft²) × price.

## Assumptions

- Each run is a rectangle; measure an L or U as separate runs that do not overlap.
- The backsplash runs along the full length of every run, in the same material.
- Slabs by area is the least that could work; seams, grain and cutouts often need one more.

## Worked examples

1. n = 2, l1 = 3.048, d1 = 0.6477, l2 = 1.8288, d2 = 0.6477, bs = 0.1016, extra = 10%, sl = 3.048, sw = 1.524, price = $60.00 gives counter = 34, backsplash = 5.333333, total = 43.266667, slabs = 1, cost = $2,596.00. Source: NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 ft² = 144 in² = 0.09290304 m², https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18); OpenStax, Prealgebra 2e, §9.4 (area of a rectangle = length × width), https://openstax.org/books/prealgebra-2e/pages/9-4-use-properties-of-rectangles-triangles-and-trapezoids (retrieved 2026-10-18).
2. n = 1, l1 = 2.4384, d1 = 0.9144, bs = 0, extra = 0%, sl = 3.048, sw = 1.524 gives counter = 24, backsplash = 0, total = 24, slabs = 1, totalM2 = 2.229673. Source: NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 ft² = 144 in² = 0.09290304 m², https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18).
3. n = 3, l1 = 3, d1 = 0.6, l2 = 2, d2 = 0.6, l3 = 1.5, d3 = 0.6, bs = 0.1, extra = 15%, sl = 3, sw = 1.4 gives totalM2 = 5.2325, slabs = 2.

## FAQ

### How do I calculate countertop square footage?

Multiply each run’s length by its depth in inches, add the runs up, and divide by 144. A 120 in run and a 72 in run, both 25.5 in deep, are (120 + 72) × 25.5 = 4,896 in², which is 34 ft².

### How do I measure an L-shaped or U-shaped counter?

Split it into rectangles that do not overlap. Measure the first run wall to end, then measure the second run from the front edge of the first run to its end, so the corner square is counted once.

### How do I add a backsplash?

Multiply the length of each run by the backsplash height. A 4 in backsplash along 192 in of counter is 192 × 4 = 768 in², or 5.33 ft². Set the height to 0 if the backsplash is tile or another material.

### How many slabs of granite or quartz do I need?

Divide the area to order by one slab’s area and round up. That is the least that could work: seams, matching veins and cutouts often need one more slab, so ask your fabricator to lay out the pieces.

### How much extra should I add?

About 10% covers sink and cooktop cutouts, seams and edge trimming. Sinks and cooktops are cut from the slab, so do not subtract them from the area you order.

### How much does a countertop cost?

Multiply the square feet to order by the installed price per square foot from your quote. At $60 per ft², 43.27 ft² costs about $2,596. Prices vary with the stone, edge profile and region.

## Sources

- OpenStax, Prealgebra 2e, §9.4 Use Properties of Rectangles, Triangles, and Trapezoids (area of a rectangle = length × width). https://openstax.org/books/prealgebra-2e/pages/9-4-use-properties-of-rectangles-triangles-and-trapezoids (retrieved 2026-10-18)
- NIST SP 811 (2008), Appendix B: 1 ft = 12 in = 0.3048 m exactly, so 1 ft² = 144 in² = 0.09290304 m². https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18)