How much kitchen worktop do I need?

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.

Worked example: an L-shaped kitchen, 3 m + 2 m

A 3 m run and a 2 m return in 600 mm-deep worktop, mitred at the corner, with a 100 mm upstand.

How we got there

1. Two runs: 3 m + 2 m = 5 m of worktop — The total run is 5 m, split into a 3 m stretch and a 2 m return.
2. The mitre adds 2 × 600 mm = 1.2 m — A mitre is cut across the depth, so the corner consumes two worktop depths — 1.2 m added to the run.
3. Run with joints: 6.2 m — The run plus the mitre allowance is 6.2 m of material.
4. Stock: 1 × 4 m + 1 × 3 m = 7.00 m — Stock comes in fixed lengths, so the order is one 4 m length and one 3 m length — 7.00 m.
5. Upstand: 2 × 3 m — A 100 mm upstand over the 5 m run is 2 lengths covering 5.00 m of wall line.

What you need to buy

The order for the worked example above, straight from this calculator's own shopping list.

• Kitchen worktop, 600 mm deep — 1 × 4 m + 1 × 3 m (7.00 m) (Covers 6.20 m of run in 2 runs. Buy the longest stock length your merchant carries — a length joined at the sink is a weak point, a single length usually is not.)
• Worktop joint bolts / connector kit — 1 kit (One kit per join. A mitred joint also wants mitre bolts or biscuits plus colour-matched adhesive.)
• Upstand / splashback panel — 2 × 3 m lengths (Covers 5.00 m of wall line at 100 mm high (0.50 m²).)
• Colour-matched joint sealant / worktop adhesive — estimate only (One tube per join, plus one for the upstand line; a sink and a hob each want a bead of silicone.)
• Worktop end panel / breakfast bar leg (optional) — as needed (An end panel closes the exposed side of a base unit; a 900 mm worktop used as a breakfast bar wants a support leg at the free end.)

Figures for the worked example only. Change the measurements above and the list recalculates.

Waste and over-ordering

Worktop is bought in stock lengths, so the waste is the offcut at the end of each length — here about 0.48 m² of the 4.2 m² ordered. A longer stock length usually wastes less than two short ones, and it removes a join. Order the joint kit and the colour-matched sealant with the worktop, not afterwards.

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.