Three quantities, not one
A countertop is quoted from three measurements and homeowners usually only carry the first one to the meeting. Square footage sets the material. Finished edge, in linear feet, sets a large part of the labour, because every exposed edge has to be shaped, polished and in some materials built up to look thicker than the slab is. Cutouts are counted individually and priced individually, because each one is a template, a cut and a polish.
The consequence is that two counters of identical area can differ substantially in price. A 120 by 25.5 inch wall run is 21.25 square feet with about 10 linear feet of finished edge, since only the front shows. An island of 84 by 42 inches is 24.5 square feet with 21 linear feet of edge, since all four sides show. Fifteen percent more material, twice the edge work.
Why the sink hole is not a discount
This is the most consistent surprise on a countertop invoice. The sink cutout removes three or four square feet of stone from the finished top, and the natural expectation is that you pay for what is left. You do not. The area is measured as installed, the removed piece is scrap that cannot be sold or reused, and there is a separate charge for cutting and polishing the opening. The same is true of the cooktop.
The reason is that the slab is consumed either way. Nothing about cutting a hole in the middle of a piece gives the fabricator material back. Understanding this before the quote arrives stops an argument, and it also changes a decision: an undermount sink and a drop-in sink consume the same material, so the choice between them is about the polished edge inside the opening and about cleaning, not about stone.
Yield, and why a slab does not go as far as its size suggests
| Situation | Yield people plan for | What eats the rest |
|---|---|---|
| Straight runs, no pattern matching | 80-85% | Saw kerf, squaring the edges of the slab, offcut strips too narrow to use |
| An L or U with a large island | 70-80% | Awkward shapes nest badly in a rectangle |
| Veining matched across a seam | 55-70% | Matching pieces have to come from adjacent stone, so half a slab may be unusable |
| A slab with a flaw or a colour shift | Whatever is left around it | Natural stone is not uniform and the supplier does not guarantee it will be |
The yield field defaults to 75 percent for that reason. If the counter is one straight run and you do not care where the pattern falls, push it up. If you are matching a book-matched island to a wall run, expect it to fall and expect the fabricator to buy the second slab.
Seams, and the two places they must not go
Slabs are finite, so a kitchen longer than a slab has seams. That is arithmetic and not negotiable. What is negotiable is where they land, and the two rules almost everyone agrees on are that a seam should not sit in the middle of the sink cutout run, and it should not cross a cooktop cutout. Both of those places are where the stone is narrowest, so a seam there sits in the weakest section, and both are where water, heat and daily use concentrate.
The good seam positions are at an inside corner, where the two pieces meet at a natural break, or in the middle of a long uninterrupted run away from any opening. Ask for a slab layout drawing before cutting. A fabricator who cuts first and shows you afterwards has made the decision for you, and stone does not come back.
Getting the measurements right in the first place
Enter finished counter dimensions including the overhang, not cabinet dimensions. A standard base cabinet is 24 inches deep, the counter typically runs 25 to 26 inches to give a front overhang past the door, and using 24 will under-order. Islands with a seating overhang are the other trap: a 42 inch island top over a 24 inch cabinet run is mostly overhang, and overhang past a certain projection needs support brackets or a corbel, which is a question for the fabricator about the specific material rather than a generic figure.
Once the top is measured, the cabinets under it are the next constraint, and they rarely divide evenly into the wall. The cabinet run and filler calculator works out which box widths actually fit the wall you have. If the backsplash is tile rather than stone, tile layout decides where the cut course lands above the counter, and the tile calculator counts the material.
Questions people ask
Do I pay for the sink cutout area on a countertop?
Yes. Countertop area is measured as installed and the cutout is not deducted, because the slab was consumed whether or not there is a hole in it and the removed piece is scrap. On top of that, most fabricators charge a separate fee per cutout for the template, the cut and the polished edge inside the opening. This catches people out reliably enough that it is worth confirming in writing when the quote arrives, along with whether the fee differs between an undermount and a drop-in sink, since the undermount opening needs a polished edge and the drop-in does not.
How many slabs do I need for a kitchen?
Divide your total square footage by the usable yield of one slab rather than by its gross size. A 120 by 60 inch slab is 50 square feet gross, but at a realistic 75 percent yield it produces about 37 square feet of finished tops, so a 60 square foot kitchen takes two slabs and not one and a bit. Yield falls further if you are matching veining across pieces, because the matching pieces have to come from adjacent parts of the same slab and the rest becomes offcut. Ask the supplier for the actual measured size of the slabs in stock, not the nominal size, since natural stone varies sheet to sheet.
Where should a countertop seam go?
At an inside corner or in the middle of a long run, and never across the sink or cooktop cutout. The narrow strips of stone in front of and behind a sink opening are the weakest part of the top, and putting a seam there puts a joint in the section that takes the most water, weight and heat. A seam at an inside corner is easier to hide because the eye reads the corner as a break anyway. The practical step is to ask for the slab layout drawing before the stone is cut, showing where each piece comes from and where the joints fall. Once it is cut, the decision is made.
Should I measure from the cabinets or the finished counter?
Finished counter, including the overhang. Base cabinets are commonly 24 inches deep and the counter usually runs an inch or two past the door face, so the counter depth is typically 25 to 26 inches. Measuring the cabinet gives a number roughly six percent low across the whole kitchen, which is enough to change the slab count on a marginal job. Islands with seating are the bigger error, because a large part of the top is overhang past the cabinet, and the overhang is stone you are buying. Note that a long unsupported overhang may need brackets, and how far is too far depends on the material and thickness, which is a question for the fabricator.
Is the backsplash included in the square footage?
Only if it is the same material, which is why there is a separate field for it. A four inch stone backsplash on 30 linear feet of counter is 10 square feet of additional material, cut from the same slab and counted in the yield. If the backsplash is tile it is a separate trade with its own arithmetic, and the layout question of where the cut course falls above the counter is handled by the tile layout calculator. A full-height stone backsplash is a much larger quantity than most people expect and often needs its own slab.