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How the worktop calculator works
Measure every run the same way: along the wall, to the corner. An L-shaped kitchen is not one long worktop bent round a corner — it is two separate lengths, each cut square, meeting at a joint. That is why the calculator asks for a second run and why it counts each run as its own board. A 3 m run and a 2 m leg is 5 m of kitchen frontage, but it is never 5 m of worktop off one board.
The mitre allowance is the part people miss. A mitred corner looks the best of the two joints and hides a wall that is a few degrees out of square, but the 45° cut across the end of the worktop removes a triangle of material the full depth of the top. On a 600 mm worktop that is 600 mm of length consumed at each end of the joint — 1.2 m on the job — which is exactly why a mitred L so often has to jump up a stock length. A butt joint, where one run simply dies into the other, needs no extra length at all.
Worktop is sold in stock lengths, not by the metre off a roll, and 3 m is the length most UK merchants carry, with 4 m in many ranges. So each cut piece takes the shortest board that covers it, and a run longer than the longest board has to be joined. The waste allowance is left at 0% on purpose: you cut worktop to the wall, and a sink or hob cut-out is made inside the board, so it takes no extra length. The offcuts are already in the order — the calculator tells you how many square metres of spare the stock lengths contain, so you can see whether a margin for a miscut is already covered.
Depth, upstands and the details that decide the finish
Depth is a property of the board you buy, not something you cut off: 600 mm is the standard UK worktop depth for a 600 mm base unit, 620 mm is the deeper trade carcass with a little more front overhang, and 900 mm is a breakfast bar or peninsula, which wants a leg or an end panel carrying the front edge rather than a base unit underneath.
An upstand of 100–150 mm finishes the joint where the worktop meets the wall and is normally cut from the same range so the colour matches. A splashback is the same idea at 600 mm high, and it only earns its keep behind a hob, a sink or a range where the wall really does take splashes. If you are tiling, skip both — but keep the worktop a few millimetres off the wall to allow for the tile and adhesive, or the top will have to come back off.
Keep any joint at least 100 mm clear of a sink or hob aperture, and leave the cut-outs to whoever fits the worktop: a router jig and a support batten are worth more here than anywhere else in the kitchen. Finally, allow the worktop to sit in the room for 48 hours before cutting and fitting, especially a timber or solid-wood top, which moves with the room's humidity.
Worktop FAQs
How much worktop do I need for an L-shaped kitchen?
Measure both runs to the corner and add them: a 3 m run plus a 2 m leg is 5 m of kitchen frontage. But an L is cut as two separate lengths, not one, and a mitred corner needs an extra 600 mm on each piece for the cut — a 3.6 m piece and a 2.6 m piece, which come off a 4 m length and a 3 m length. That is 7 m of stock for 5 m of kitchen, and the offcuts are what pay for the corner.
Should I mitre the corner or butt the joint?
A mitre looks better, hides a wall that is a few degrees out of square, and keeps the grain running diagonally through the corner — but it costs a full worktop depth of length at each end, so 1.2 m extra on a 600 mm top, and it has to be cut accurately and pulled up hard with mitre bolts and adhesive. A butt joint uses no extra length at all and is the usual choice for a cheaper laminate top, where the join is small enough to hide behind a corner unit.
What depth is a standard kitchen worktop?
600 mm is the standard UK worktop depth and matches a 600 mm base unit carcass with a small overhang at the front. 620 mm is the deeper trade carcass, giving roughly 20 mm more usable surface, and 900 mm is a breakfast bar or peninsula — deep enough to sit at, and it needs a support leg at the free end rather than a base unit underneath.
Do worktops come in a 4 m length?
3 m is the length most UK merchants stock, with 4 m available in many ranges — so ask before you measure up, because it changes the order completely. A 5 m straight run cannot be bought as one piece at either length: it needs two 4 m lengths, one of which is cut down, and the surplus is 3 m of spare worktop. Where a run is over 4 m it is usually cheaper to shorten the kitchen with a taller unit than to pay for the second length.
Do I need an upstand or a splashback?
Not if you are tiling, but an upstand is the neatest way to finish the joint where the worktop meets the wall. An upstand is 100–150 mm high and a splashback is the same material at 600 mm; both are sold in 3 m lengths and are cut from the same run, so a 2.4 m run at 100 mm is 0.24 m² and one 3 m length. A splashback only earns its place behind a hob, a sink or a range where the wall takes splashes.
How much extra should I allow for sink and hob cut-outs?
None for the length. A cut-out is made inside the worktop, so it takes no extra metres — that is why this calculator leaves the waste allowance at 0% by default. What the cut-outs do need is room and support: keep any joint at least 100 mm clear of a sink or hob aperture, and check the fitting instructions, because most hobs need 50 mm of worktop at each end and a hob or sink cut-out in a laminate top wants a heat-resistant mat under the hot pan.
Regs & planning for this calculator
Worktop runs are constrained by clearance first and by the worktop itself second.
- Approved Document M — access and clearance A 1200 mm clear space in front of and between kitchen units in a visitable dwelling, 1500 mm in an accessible and adaptable one, and minimum worktop lengths by number of bedspaces. Read the requirement.
- Approved Document P — electrical Socket positions near a bath or shower, and the fact that replacing a consumer unit is one of the three notifiable jobs. Read the requirement.
- BS 7671 — the Wiring Regulations The standard Part P points at, which governs the circuits behind the units. Read the requirement.