How this calculator works
Each run is a straight length along a wall. A board covers one board length, so a run takes the length divided by the board length, rounded up. Where a run is longer than a board there is a join along it. At a corner the boards are joined in one of two ways. A mitre joint runs both boards to the corner and cuts them at 45 degrees, so each run is cut to its full wall length. A butt joint runs the first board to the corner and stops the second against its side, so the second board is shorter by the depth of the worktop.
Worked example: runs of 3.6 m and 2.4 m with mitre corners, 3 m boards and a 600 mm depth need 3 boards: two for the 3.6 m run, which gets one straight join, and one for the 2.4 m run, plus one corner joint, so 2 joints and 3.60 m². With a butt joint the second run is cut to 1.80 m, which is still 3 boards. With 4.1 m boards the same kitchen takes 2, and with a third run of 3 m on a U-shaped plan it takes 4 3 m boards.
Assumptions and sources
- Assumptions used: mitre corners, so every run is cut to its full wall length; each run is cut from its own board or boards, and the offcut is not used elsewhere; no allowance for overhang at open ends or for waste.
- Measure along the back wall of each run from the corner. Walls are rarely square or straight, so most worktops are cut to a scribed line at the wall and the length of a mitre depends on the true angle: measure again after the units are fixed. If a run ends at an open end, add the overhang that you want (often 20 to 25 mm) to the run length. Cutting hole for a hob or sink takes the template and the manufacturer's sizes, and the material and its thickness change how the corner is made: laminate and solid wood are mitred with a router jig, while stone is cut and polished by the fabricator.
The formula and a worked example are shown above, so you can check any result by hand. Read how we calculate and check our numbers. Results are estimates for planning: supplier products vary, so check the size printed on the label.
Worktop boards for common kitchens
Mitre corners, 600 mm deep, 3 m and 4.1 m boards.
| Kitchen | Boards (3 m) | Boards (4.1 m) | Joints (3 m) | Area |
|---|---|---|---|---|
| 2.4 m | 1 | 1 | 0 | 1.44 m² |
| 3.6 m | 2 | 1 | 1 | 2.16 m² |
| 3.6 + 2.4 m | 3 | 2 | 2 | 3.60 m² |
| 4.2 + 3 m | 3 | 3 | 2 | 4.32 m² |
| 3.6 + 2.4 + 3 m | 4 | 3 | 3 | 5.40 m² |
Tips before you buy
- Keep a joint away from the sink and the hob. Water and heat attack a joint, and most makers say not to put one over a sink or a dishwasher.
- Check the walls with a long straight edge and a square before you order. If a wall is out of square the mitre will not close, so it is better to scribe.
- For a mitre joint, use a router jig and the joint bolts that suit the thickness of the worktop, seal the cut edges and the joint with the sealant the maker names.
- Seal every cut edge, especially round the sink and hob cut-outs. Chipboard core swells if water gets in.
- Support the worktop on the full depth of the units and fix it from below with brackets or screws that do not go through the top.
Tools & materials for this project
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Frequently asked questions
How many worktops do I need for my kitchen?
Divide the length of each run by the board length and round up. Runs of 3.6 m and 2.4 m with 3 m boards need 3 boards, and 2 boards if you use 4.1 m ones.
What length are kitchen worktops?
Laminate worktops are commonly sold in 3 m and 4.1 m lengths, 600 mm deep and 38 mm thick. Other materials and makers have other sizes, so check the product.
How is a corner in a worktop joined?
With a mitre joint, cut at 45 degrees and pulled tight with bolts under the worktop, or a butt joint where the second board meets the side of the first. A mitre joint is more common on laminate and wood.
How long is the second run with a mitre joint?
The full wall length. With a butt joint it is cut short by the depth of the worktop at each corner, which is 600 mm.
Where should the joints go?
Away from the sink, the hob and the dishwasher. Joints are the weak points where water and heat do the damage.
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Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.