How do I calculate countertop square footage?

Measure each straight run on its own, multiply its length in feet by its depth in inches, divide by twelve, and add the results. The mistake almost everybody makes is treating the kitchen as one rectangle. It is not: the sink run, the return around the corner, the strip beside the range and the island all have different lengths, and the island usually has a different depth as well because it carries a seating overhang. Multiply one length by one depth and you can be out by a third.

What is a standard countertop depth?

25.5 inches is the depth stock post-formed countertop is sold at in Ontario, which makes it the one figure in this range you can go and check on a shelf. It comes from a 24 inch base cabinet plus the overhang at the front. A bathroom vanity is usually shallower at around 22 inches, and an island with seating is deeper again, commonly 36 to 42, because the overhang people sit at is added to the working depth. Measure yours rather than assuming, especially in an older house.

Why does this give me linear feet as well as square feet?

Because a fabricator prices two different things off two different measurements, and a quote that only mentions one of them is incomplete. The material and the fabrication of the surface are priced by the square foot. The edge profile is priced by the linear foot, and so is fabrication on some quotes. If you walk in with square feet only, you cannot check the edge line, which on a premium profile across twenty feet is a four-figure number.

Do I include the sink cut-out in the square footage?

Yes. Fabricators charge for the full slab area and then charge again for cutting the hole, because the material inside the cut-out was bought, handled and thrown away. It is not a saving and no shop will deduct it. The same is true of the cooktop opening. Deducting cut-outs from your own measurement is a reliable way to arrive at a number lower than every quote you receive and to spend a week wondering why.

How long can a countertop be before it needs a seam?

Longer than the slab is longer than one piece, and slabs are finite. HanStone Quartz, which manufactures in Ontario, publishes its jumbo slab at 65 by 130 inches, so 130 inches, or 10 feet 10 inches, is the longest single run that can come off one of them. Natural granite is quarried rather than made, so its sizes vary more and are usually smaller. This calculator flags any run longer than the published jumbo length, because a seam you were told about before the quote is a design decision and one you find out about afterwards is a complaint.

Is this number good enough to order from?

No, and no honest tool would say otherwise. Countertop Installers built this so you can compare quotes and sanity-check the square footage somebody has already given you, which is exactly what a homeowner needs it for. Nobody cuts stone to a tape measurement taken by the person who lives there. A fabricator will digitally template the room, and the template is what gets cut, because walls are not straight and cabinets are not square.

Kitchen countertop square footage calculator

Last updated: August 25, 2026By The Slab Desk

People do not get this wrong because the arithmetic is hard. They get it wrong because a kitchen counter is not one rectangle, and treating it as one is out by a third in whichever direction rounds against you. Measure each straight run on its own and this adds them up, in all three of the units a fabricator will ask you for.

One row per straight run

This is where people go wrong, and it is not the arithmetic. A kitchen counter is almost never one rectangle: it is a run at the sink, a return round a corner, a strip by the range and an island, and they do not share a depth. Measure each straight piece on its own.

SectionLength (ft)Depth (in)
21.3 sq ft
21.25 sq ft
SectionLength (ft)Depth (in)
12.8 sq ft
12.75 sq ft
SectionLength (ft)Depth (in)
26.7 sq ft
26.67 sq ft

Common depths: 25.5 in kitchen counter, 22 in bathroom vanity, 40 in island with seating

Square feet

60.7

What the material is priced by.

Linear feet

What the edge profile and the fabrication are priced by.

Square metres

5.64

Plenty of Canadian slab is specified metric.

3 measured sections, section by section
Section	Length x depth	Area
Sink run	10 ft x 25.5 in	21.25 sq ft
Range wall	6 ft x 25.5 in	12.75 sq ft
Island	8 ft x 40 in	26.67 sq ft

Measure to the wall, not to the cabinet, and include the overhang at the front. A fabricator will template the room properly before cutting anything, so treat this as the number you use to compare quotes rather than the number anybody cuts to.

Measuring it properly, in the order that matters

Break the kitchen into straight pieces first, before touching a tape. Walk it and count the runs. Most kitchens have three or four. An L is two runs, not one, and a U is three.
Measure each run wall to wall, not cabinet to cabinet. The counter goes to the wall. Measuring the cabinet run loses you the scribe at each end, and on a three-run kitchen that adds up.
Measure depth including the overhang at the front. The overhang is stone you are buying. On an island it is often several inches of it, all the way along.
Where two runs meet at a corner, count the corner once. Run one to the corner and start run two from the inside face, or you will pay for the same square foot twice on paper and then argue about it.
Do not deduct the sink or the cooktop. That material was bought, handled and thrown away, and no shop will credit it back.

The seam warning uses a published figure rather than a rule of thumb. HanStone Quartz manufactures in Ontario and lists its jumbo slab at 130 by 65 inches, so 130 inches is the longest single piece that can come off one. Natural granite is quarried rather than made, so its sizes vary and are often smaller, which means a run that just fits on quartz may not fit on the granite you have picked. Ask about the actual slab.

Sources

HanStone Quartz Canada, colour spec page - Jumbo quartz slab, HanStone Quartz (manufactured in Ontario), length: 130 inches
HanStone Quartz Canada, colour spec page - Jumbo quartz slab, HanStone Quartz (manufactured in Ontario), width: 65 inches
The 25.5 inch counter depth is the depth of the stock post-formed countertop sold in Ontario, published by Home Depot Canada and recorded in this site's laminate cost guide.

Frequently asked questions

How do I calculate countertop square footage?: Measure each straight run on its own, multiply its length in feet by its depth in inches, divide by twelve, and add the results. The mistake almost everybody makes is treating the kitchen as one rectangle. It is not: the sink run, the return around the corner, the strip beside the range and the island all have different lengths, and the island usually has a different depth as well because it carries a seating overhang. Multiply one length by one depth and you can be out by a third.
What is a standard countertop depth?: 25.5 inches is the depth stock post-formed countertop is sold at in Ontario, which makes it the one figure in this range you can go and check on a shelf. It comes from a 24 inch base cabinet plus the overhang at the front. A bathroom vanity is usually shallower at around 22 inches, and an island with seating is deeper again, commonly 36 to 42, because the overhang people sit at is added to the working depth. Measure yours rather than assuming, especially in an older house.
Why does this give me linear feet as well as square feet?: Because a fabricator prices two different things off two different measurements, and a quote that only mentions one of them is incomplete. The material and the fabrication of the surface are priced by the square foot. The edge profile is priced by the linear foot, and so is fabrication on some quotes. If you walk in with square feet only, you cannot check the edge line, which on a premium profile across twenty feet is a four-figure number.
Do I include the sink cut-out in the square footage?: Yes. Fabricators charge for the full slab area and then charge again for cutting the hole, because the material inside the cut-out was bought, handled and thrown away. It is not a saving and no shop will deduct it. The same is true of the cooktop opening. Deducting cut-outs from your own measurement is a reliable way to arrive at a number lower than every quote you receive and to spend a week wondering why.
How long can a countertop be before it needs a seam?: Longer than the slab is longer than one piece, and slabs are finite. HanStone Quartz, which manufactures in Ontario, publishes its jumbo slab at 65 by 130 inches, so 130 inches, or 10 feet 10 inches, is the longest single run that can come off one of them. Natural granite is quarried rather than made, so its sizes vary more and are usually smaller. This calculator flags any run longer than the published jumbo length, because a seam you were told about before the quote is a design decision and one you find out about afterwards is a complaint.
Is this number good enough to order from?: No, and no honest tool would say otherwise. Countertop Installers built this so you can compare quotes and sanity-check the square footage somebody has already given you, which is exactly what a homeowner needs it for. Nobody cuts stone to a tape measurement taken by the person who lives there. A fabricator will digitally template the room, and the template is what gets cut, because walls are not straight and cabinets are not square.