Key Takeaways
- Allow 1,000 to 1,200 mm of clearance on every side. 900 mm is the absolute floor.
- Smallest island worth building: 1,000 x 1,000 mm. Most are 1,800 to 2,400 mm long by 1,000 to 1,100 mm deep.
- Minimum room width: 3,650 mm for one run plus an island, 4,300 mm with units on both walls.
- Seating needs 600 mm per stool and a 300 mm overhang.
- Worktop height is 900 mm: 720 mm carcass, 150 mm legs, 30 to 40 mm top.
Most island decisions are settled by a tape measure long before anyone opens a brochure. Here are the dimensions that decide whether your kitchen can take one, in millimetres, so you can check the room this afternoon.
How much space does a kitchen island need?
Allow 1,000 to 1,200 mm of clear floor on every side you use. 900 mm is the absolute minimum, and only where no appliance doors open onto it. Past 1,500 mm the island is no longer reachable from the run behind you.
Appliance doors catch people out. A dishwasher door drops around 500 mm into the room and an oven door swings 500 to 550 mm, so at 900 mm you have 350 to 400 mm to stand in. Hence 1,050 mm on any side with an oven or dishwasher.
| Clearance | Verdict | Why |
|---|---|---|
| Under 900 mm | Do not | Two people cannot pass, doors foul the island |
| 900 mm | Bare minimum | One cook, no appliance doors that side |
| 1,000 to 1,200 mm | The right answer | Two people pass, oven and dishwasher doors clear |
| Over 1,500 mm | Wasteful | Island no longer reachable from the run |
What is the minimum room width for an island?
Add the parts up and the answer is fixed. A 650 mm worktop run, 1,000 mm of clearance, a 1,000 mm deep island and 1,000 mm on the far side comes to 3,650 mm wall to wall. Units down both walls needs 4,300 mm. Squeezed to the minimum, 3,450 mm and 4,000 mm.
That is why islands rarely fit an unaltered London terrace. A Victorian rear reception is commonly 3,300 to 3,700 mm internally, so the island only appears once a side return infill takes the room out to 4,200 to 5,000 mm. Under 3,600 mm, fit a peninsula instead: it needs clearance on two or three sides rather than four, which buys back a full metre. See small kitchen ideas.
What size should the island itself be?
The smallest island worth the floor it eats is 1,000 x 1,000 mm. Most end up 1,800 to 2,400 mm long and 1,000 to 1,100 mm deep, the size three or four 600 mm base units plus an overhang produce.
| Dimension | Figure | Note |
|---|---|---|
| Minimum useful size | 1,000 x 1,000 mm | Below this it is a table |
| Typical size | 1,800 to 2,400 x 1,000 to 1,100 mm | Three or four 600 mm units |
| Maximum depth | 1,200 mm | You cannot reach the middle from one side |
| Longest single piece | Around 3,000 mm | Beyond this the worktop carries a joint |
| Worktop height | 900 mm | 720 mm carcass, 150 mm legs, 30 to 40 mm top |
| Pendants above the top | 750 to 900 mm | Keeps sightlines and heads clear |
Slab size drives that last row: quartz and granite come from blanks around 3,000 to 3,200 mm long. Our worktop comparison covers how each material handles a joint.
How much overhang do you need for seating?
Allow 600 mm of width per stool and a 300 mm overhang for knees, so a 2,400 mm island seats four along one side and an 1,800 mm island seats three.
- Overhang: 250 mm is tight, 300 mm right, 380 mm suits a full place setting.
- Support: past roughly 300 mm of unsupported stone, fabricators want brackets or a steel flat bar.
- Stools: a 900 mm worktop takes a 600 to 680 mm seat height, not a 750 mm bar stool.
- Behind: 900 mm clear so people can get off them.
What to put in it
- Storage and worktop: the only option with no services running to it.
- Sink: sociable, but needs hot, cold and a waste under the floor.
- Hob: striking, but needs a dedicated circuit and downdraft or ceiling extraction.
- Seating: 600 mm per stool, 300 mm overhang.
Mind the services
The waste is the awkward one. A 40 mm waste needs a fall of roughly 18 to 44 mm per metre, so a 4 m run to the stack drops 70 to 175 mm. A suspended timber floor with 200 mm joists absorbs that; a ground-floor slab does not, and you are into chasing it or raising the floor. Far easier during a full kitchen renovation, when the floor is up.
An island hob must also satisfy extraction. Approved Document F asks for 30 litres per second adjacent to the hob, or 60 litres per second elsewhere, so a recirculating downdraft is a compromise to make deliberately.
Approved Document F, Ventilation (gov.uk, 2026 edition); waste gradients from UK wet trade guidance, 2026.Islands and open-plan
In an open-plan kitchen-diner, the island divides cooking from living. Set it parallel to the run and face the 1,200 mm side towards the living area, so the main route through the room is the generous one. See our lighting guide.
What does an island cost in London?
A storage island of three or four units with a quartz top runs £2,500 to £6,000 within a wider kitchen. Add a sink, waste and power and it is £4,000 to £9,000, because the floor comes up.
Indicative London ranges from GS Renovation project pricing, benchmarked against MyJobQuote and Rated People 2026 unit and worktop rates.We design and build kitchens and islands across London: see kitchen renovation London, or contact us on 07472 424 226.