Kitchen Countertop Calculator

How the kitchen countertop calculator works

Measure every run of base cabinets along the back wall, right into each corner, and add the lengths together. That total is the run. Where two legs of an L meet, both measurements include the same square of counter in the corner, one depth by one depth. Count it twice and you pay for it twice. So the calculator takes one counter depth off for every corner, then adds your waste allowance:

ℓ = (L − k × W) × (1 + w)

L is the total run, k the number of corners, W the counter depth and w the waste as a decimal. The finished surface area is the net length times the depth, before waste. Cost is the length to order times your price per linear foot or metre.

An L-shaped kitchen, worked through

Take an L with an 8 ft leg and a 5 ft leg, measured along the walls, with the usual 25.5 in counter. The run is 13 ft. One corner comes off: 25.5 in is 2.125 ft, so the net length is 13 − 2.125 = 10.875 ft. Check it by thinking about the pieces. The long leg runs the full 8 ft into the corner; the short leg butts against its front edge and only needs 5 − 2.125 = 2.875 ft. Together, 10.875 ft.

With 10% waste that is 11.96 ft to order, and the finished top covers 10.875 × 2.125 = 23.1 ft². At $60 a linear foot the estimate is $717.75.

The metric default is the same shape: legs of 2.4 m and 1.6 m, so 4 m of run, 600 mm deep, one corner. Net length is 4 − 0.6 = 3.4 m, 3.74 m with 10% waste, and 3.4 × 0.6 = 2.04 m² of finished surface. At the default price of 120 a metre, in whichever currency the page shows, that comes to 448.80.

Standard counter depths

In the US, base cabinets are 24 in deep and the counter usually sits at 25 to 25.5 in so it overhangs the doors. The NKBA Kitchen Planning Guidelines plan counter space in 24 in deep frontage and recommend 158 in of it in total for a working kitchen. Elsewhere, 600 mm is the standard worktop depth, with 900 mm boards sold for breakfast bars and islands, as this laminate worktop guide sets out. Enter what your cabinets actually need: deeper-than-standard units, or a thicker front edge that needs more overhang, change the numbers.

Corners, joints and why the joint type matters

A butt joint or a mason's mitre on laminate uses the net length the calculator gives you. One piece runs through into the corner, and the other stops at its front edge, give or take the short mitred return at the front. Worktop Express's installation instructions describe both the 90° joint and the 45° mitre, and ask for three bolts across a 600 mm joint and four across a 900 mm one.

A full 45° diagonal mitre is different. Each piece is cut from a blank as long as its whole leg, and the triangles cut off are waste. If you are mitring solid wood or stone that way, add one depth per corner back on to the length you buy. The finished area does not change.

Stock lengths and slabs

Laminate and solid wood come in fixed lengths, so the length to order is a minimum, not a shopping list. Every leg of an L or U is its own piece, and any leg longer than the longest board needs a join along it too. So plan pieces, not totals. In the metric example the pieces are 2.4 m and 1.0 m: one board of 3.5 m or more takes both, but a 3 m board does not, because its 0.6 m offcut is too short for the second leg. Joins look best away from the sink and hob.

Quartz and granite are usually priced by area. That is what the price per ft² (or m²) row is for: it turns your linear rate into an area rate so you can compare it with a fabricator's quote. A fabricator will template the kitchen, lay the pieces out on whole slabs and quote from that, so for stone the calculator is a budget, and the slab count is theirs to decide.

Choosing the waste allowance

The default is 10%. It covers trimming ends, scribing to a wall that is out of true, and cutting sink and hob openings from a board that already has an offcut at one end. A straight run in a square room can go lower. Several short legs, an island with an odd length, or your first attempt at cutting laminate justify more. For stone, you can set it to zero and let the fabricator's layout carry the waste.

Measuring without mistakes

Measure at the back wall, not the cabinet fronts, and measure every leg into the corner even though the pieces themselves will be shorter. The calculator does the deduction. Include end overhangs past the last cabinet; the Wickes fitting guide works with a 20 mm overhang at exposed ends and a small one at the front. Where a leg ends at a tall unit or an appliance housing, stop at its side. Count only the corners where two counters meet. A counter that simply stops at a wall is not a corner. An island or bar that is deeper than the wall runs belongs in a separate calculation, because the depth applies to the whole run.

What this tool does not do

It does not lay pieces out on stock lengths or slabs, allow for backsplash upstands, or price cut-outs, edge profiles and fitting. Those vary by supplier and are worth asking for line by line. Moving a sink or hob can also mean new plumbing, gas or electrical work, which needs a licensed or registered installer wherever you are.

Using this calculator with other BuildMetricLab tools

The kitchen cabinet calculator counts the base units under the counter, and the backsplash calculator covers the wall above it. All BuildMetricLab tools run in your browser with no sign-up, and the formula is on the page so the maths can be checked.