Flat-pack vs fitted kitchen: what's the real cost difference?

The short answer

A flat-pack kitchen with stock cabinets typically costs £7,650 fitted. Step up to semi-custom cabinetry and the typical cost rises to £7,800, while a fully custom kitchen typically comes to £9,350. All three figures are for a standard 4.5 m run with fitting included; worktops, appliances, splashbacks and lighting sit on top. Across a whole project, that puts a basic kitchen at £4,900 and a premium one at £9,250 — see our full New kitchen for the complete breakdown by tier.

What "flat-pack" actually buys you

Flat-pack, or stock, cabinets are mass-produced to a handful of standard widths (usually 50 mm or 100 mm increments) and shipped boxed for a fitter to assemble on site. The carcasses are typically melamine-faced chipboard, doors are a limited range of laminate or painted MDF finishes, and runs are built up from standard units rather than a bespoke plan for your room.

The saving isn't really in the materials — it's in the design and manufacturing time. There's no bespoke drawing, no made-to-measure panels, and assembly is quick for an experienced fitter. That's why labour makes up a smaller share of a stock-cabinet job than a custom one.

The trade-off shows up when your kitchen isn't a neat rectangle. Awkward corners, sloping ceilings, services boxed in at odd angles, or a run that doesn't divide cleanly into standard widths all mean filler panels, cut-down units, and compromises on storage. None of that is visible on a showroom price list.

What semi-custom and custom actually change

Semi-custom cabinets are still factory-made but offer made-to-measure widths, more finish and colour choices, and better-quality box construction (often plywood rather than chipboard, soft-close as standard). This is where most mid-range kitchens land, and it's usually the point where a run can be designed to fit the room exactly rather than the room being adapted to fit standard units.

Custom cabinetry is built or finished to your drawings: any width, any configuration, integrated appliance housings, bespoke internal storage. The cost difference between semi-custom and custom is less about the boxes themselves and more about design time, joinery labour, and often solid-wood or painted-in-frame doors rather than foil or laminate.

Where the real cost difference shows up

• Fitting time. Stock units go together fast; custom runs involve more site measuring, more cutting, and more adjustment as the job progresses.
• Waste and filler panels. A room that doesn't match standard cabinet widths needs fillers with stock units — effectively paying for cabinet you can't use.
• Longevity of hinges and drawer runners. Cheaper stock ranges often use basic hardware that wears faster under daily use; semi-custom and custom ranges tend to specify better-rated soft-close mechanisms.
• Resale and finish. A custom kitchen designed around your layout is harder to compare directly to a competitor's quote, since no two are built the same way — this is exactly the kind of job worth running past our "is my quote fair" tool before you sign anything.

When flat-pack is the sensible choice

If your kitchen is a standard shape, you're not short on budget-stretch storage needs, and you're planning to move within a few years, stock cabinets are a legitimate way to keep costs down without a lower-quality result — the carcass quality on a well-specified stock range is perfectly serviceable. Where flat-pack struggles is in galley kitchens, loft or extension kitchens with sloping ceilings, or anywhere services (boilers, meter cupboards, soil stacks) box into the run in a way standard widths weren't designed around.

When fitted pays for itself

Semi-custom earns its premium fastest in awkward rooms, where filler panels and wasted stock units would otherwise eat into the saving. Custom cabinetry tends to pay off when you're maximising storage in a small kitchen, integrating appliances fully, or specifying a door finish (in-frame painted, for example) that isn't available off the shelf at all. If you're also replacing the floor as part of the job, it's worth pricing that separately — see our New flooring guide, since kitchen flooring is usually quoted and fitted as its own trade.

How we calculate this

Our kitchen figures are built from labour hours for design, cabinet fitting, worktop templating and installation, electrical and plumbing first-and-second fix, multiplied by local UK trade rates, plus current material costs for each cabinet tier and worktop option. We check the results against market prices and real quotes before publishing, and update them as material and labour costs move. For the materials that make the biggest difference to your total — worktop choice, cabinet tier, and appliance package — use the New kitchen cost guide to model your own kitchen before you start getting quotes in.