Standard Kitchen Unit Measurements: Hardware Sizing Guide
When planning a kitchen refurbishment or fitting replacement hardware, precise sizing is essential. In the UK, standard kitchen unit measurements follow modular joinery conventions designed to ensure components work together seamlessly. However, external carcass dimensions do not tell the whole story. Understanding carcass board thickness, internal clearance, and service voids is critical before purchasing drawer slides, hinges, or pull-out storage solutions.
UK Base and Wall Unit Dimensions
Kitchen carcasses in the UK are built around standard modular widths. Understanding these external sizes allows you to accurately determine the internal capacity for fittings.
- Base Units: Typically 720 mm high (excluding adjustable plinth feet, which add 100 mm to 150 mm) and 560 mm to 600 mm deep overall. Standard modular widths range from 300 mm to 1000 mm in 100 mm increments, alongside 150 mm pull-out units.
- Wall Units: Usually 720 mm or 900 mm high and 300 mm to 350 mm deep, avoiding clash points with worktop workspaces below.
- Carcass Board Thickness: Most UK manufacturers construct carcasses from 18 mm or 15 mm MFC (melamine-faced chipboard). Always measure your cabinet walls; this 3 mm difference per side significantly impacts internal drawer and wirework clearance.
Selecting Drawer Runners by Carcass Depth
Drawer runner lengths depend entirely on internal carcass depth, not the total worktop depth. A standard base unit usually accommodates drawer runners between 450 mm and 500 mm in nominal length.
Standard base units often feature an internal depth of around 500 mm to 520 mm to allow for a 40 mm to 50 mm service void at the back for plumbing and wiring. Consequently, 450 mm or 500 mm runners are the standard choice for full-extension or soft-close drawer boxes. For shallow wall units or bespoke larder cabinets, shorter runner profiles (such as 250 mm to 300 mm) are necessary.
Choosing Internal Wirework and Pull-Out Storage
Pull-out larders, corner carousels, and under-counter wire baskets are engineered for specific cabinet widths. Because external kitchen unit measurements include both carcass side panels, you must verify the internal clear width:
| External Cabinet Width | Internal Width (18 mm Carcass) | Internal Width (15 mm Carcass) |
|---|---|---|
| 300 mm | 264 mm | 270 mm |
| 500 mm | 464 mm | 470 mm |
| 600 mm | 564 mm | 570 mm |
Ensure any side-mounted baskets or pantry mechanisms feature spacer blocks if the unit doors do not open past 90 degrees, preventing the fittings from catching on the door seals or hinge arms.
Hinges, Overlays, and Drilling Positions
Concealed cup hinges standardise on a 35 mm diameter bore hole drilled into the reverse of the cabinet door. However, the hinge plate mounting and crank angle depend directly on the carcass arrangement:
- Full Overlay: The door covers the full edge of an 18 mm carcass wall (with a standard 2 mm reveal). This is standard for modern modular kitchens.
- Half Overlay (Twin): Used where two adjacent doors share a single central 18 mm partition wall.
- Inset: The door sits flush inside the carcass frame, requiring dedicated inset hinges and mounting plates.
Frequently Asked Questions
What is the standard drilling pattern for UK kitchen carcasses?
Most modern units follow the 32 mm system. This consists of vertical rows of 5 mm shelf-support and hinge-plate holes spaced 32 mm apart, set 37 mm back from the front carcass edge.
How do I account for a service void when buying hardware?
Always measure the usable internal depth from the front carcass edge to the internal backboard, rather than measuring the exterior depth to the wall.