The short answer
Unit cost is driven mainly by carcass thickness (18mm rigid lasts and feels better than 15mm flat-pack), whether units arrive rigid or flat-pack, the hinges and runners (soft-close vs basic), and the door finish. Together these explain most of the price difference between a budget and a mid-range kitchen. See the luxury vs budget guide for how units fit into the wider tiers.
The units, or cabinets, are the backbone of a kitchen and a large part of its cost. Understanding what makes one unit cost twice another helps you read a quote and decide where to spend. This guide explains the carcass, the doors, the moving parts and the configuration choices that drive unit cost.
Kitchen units at a glance
- Carcass thickness 15mm vs 18mm
- Build type Flat-pack vs rigid (pre-built)
- Hinges / runners Basic vs soft-close
- Door finish Foil / painted / timber / lacquer
- Cost per unit (supply & fit, mid-range) £250–£600
- Specialist storage Larders, corners, pull-outs add cost
Carcass: the box behind the doors
The carcass is the structural box of each unit. The two common thicknesses are 15mm and 18mm. An 18mm carcass is stronger, holds its shape better under a heavy stone worktop, and resists sagging over years of use; 15mm is lighter and cheaper and is fine for lighter-duty budget kitchens. The carcass material is usually melamine-faced chipboard or MDF; better units use moisture-resistant board, which matters in a room full of steam and spills. The carcass is the part you rarely see but live with longest, so it is a sensible place to spend if your budget allows.
Rigid vs flat-pack
Flat-pack units arrive in pieces and are assembled on site or in advance; rigid units arrive already built. Rigid units are generally squarer, stronger and quicker to fit, and tend to indicate a better-quality kitchen. Flat-pack is cheaper and is what most budget ranges supply. The difference shows over time: a rigid carcass stays true, while a poorly assembled flat-pack can rack or loosen. The choice affects both the unit price and the fitting time — see our labour cost guide.
| Feature | Budget unit | Mid-range / luxury unit |
|---|---|---|
| Carcass | 15mm flat-pack | 18mm rigid |
| Board | Standard chipboard | Moisture-resistant board |
| Hinges | Basic | Soft-close, adjustable |
| Drawers | Single-wall, basic runners | Metal-sided, soft-close, full-extension |
| Doors | Foil-wrapped MDF | Painted, timber or lacquered |
Doors, drawers and the parts that move
Doors are the most visible element and the biggest driver of how a kitchen looks. Foil-wrapped MDF is the budget standard; painted and laminate fronts sit in the middle; solid timber, in-frame and lacquered doors are premium. The moving parts matter just as much for daily use: soft-close hinges and full-extension, soft-close drawer runners are a noticeable upgrade and are standard from mid-range upwards. Drawer boxes themselves range from basic single-wall to robust metal-sided systems that carry more weight and slide smoothly for years.
Specialist units and storage
Beyond standard base and wall units, kitchens use specialist cabinets that add cost but earn their place: tall larder units, corner carousels and magic-corner pull-outs, pan drawers, bin units and internal drawer fit-outs. These are where a well-designed kitchen makes a small room work hard, and where a luxury kitchen spends on internal organisation. See our planning guide for how to use storage well.
How units appear in a quote
A good quote specifies the unit range, the carcass thickness and build type, the hinge and runner brand, and the door finish, so you can compare like with like. If a quote simply says “kitchen units” without detail, ask for the specification — a cheaper quote on flat-pack 15mm units is not comparable with one on rigid 18mm units. See our guide on choosing a kitchen fitter. This is general information; unit specifications and costs vary with the range and supplier you choose.
Compare kitchen quotes
Unit specification is where quotes most often differ. Compare itemised quotes from kitchen design and fitting specialists in your area.
Frequently asked questions
What is the difference between rigid and flat-pack kitchen units?
Rigid units arrive already built and are squarer, stronger and quicker to fit; flat-pack units arrive in pieces and are assembled on site. Rigid generally indicates a better-quality kitchen and stays true over time, while flat-pack is cheaper and standard in budget ranges.
Does carcass thickness really matter?
Yes. An 18mm carcass is stronger, holds its shape under a heavy worktop and resists sagging over years; 15mm is lighter and cheaper and suits lighter-duty budget kitchens. The carcass is the part you live with longest, so it is a sensible place to spend.
Are soft-close doors and drawers worth it?
Most people find them worth it — they are quieter, gentler on the units and a noticeable daily improvement. They are standard from mid-range upwards and can usually be added to budget ranges for a modest extra cost.
Can I replace just the doors instead of the whole kitchen?
If the carcasses are sound and the layout still works, replacing doors and worktops can refresh a kitchen for much less than a full replacement. It only makes sense where the units underneath are in good condition; worn or damaged carcasses are better replaced.
Sources & further reading
- KBSA (Kitchen Bathroom Bedroom Specialists Association) — guidance on kitchen units and specification
- GOV.UK / Building Regulations Approved Document P — electrical safety in dwellings
- Gas Safe Register — rules for gas hob connections
- TrustMark — finding and checking registered tradespeople
This is general information, not advice for your specific property or installation. Costs, specifications and outcomes vary with the range, supplier and specialist you choose.