What are the standard sizes of kitchen units?

Kitchen dimensions look like a standard and behave like a convention. The depth, the worktop height and the width increments are close enough to universal that appliances and worktops interchange. Carcass heights, door sizes and drawer front heights are not, and assuming they are is how people order forty doors that do not fit.

Step by step

1. Start with worktop height, because it sets everything.Around 900mm from floor to worktop surface is the British convention: a 720mm carcass, 150mm of leg, and a worktop of 30 to 40mm. Adjustable legs give roughly 100 to 200mm of range, so the height is a choice rather than a fixed number.
2. Take base unit depth as 600mm, but measure the run.600mm is the nominal carcass depth, and it is what integrated appliance housings are designed around. The worktop is usually 600mm or 620mm deep and overhangs the door fronts at the front and leaves a service gap at the back.
3. Read widths in 100mm steps.300, 400, 500, 600, 800 and 1000mm are the common base unit widths. 500 and 600 dominate. A 1000mm unit is normally a double door or a corner unit. Anything that is not one of these is a filler panel doing a job.
4. Treat 600mm as the appliance module.Freestanding cookers, dishwashers, washing machines and most fridge-freezers are built to fit a 600mm gap. Integrated appliances fit a 600mm housing. Slimline dishwashers are 450mm. This is the dimension you cannot compromise on when planning.
5. Check wall unit depth and height separately.Wall units are typically 300 or 350mm deep. Heights vary far more — 575, 720 and 900mm are all common, because the height is chosen to line the tops up with a tall unit. There is no universal answer here.
6. Assume the gap between worktop and wall units is a choice.Somewhere around 450 to 600mm is usual. It is not standardised, and it is set by what goes on the worktop, by the extractor above the hob, and by the height of the person using the kitchen.
7. Measure your own carcass before buying doors.Carcass heights of 715, 720 and 725mm all exist, and door heights differ correspondingly. Measure an existing door in both directions and measure the hinge cup position from the top of the door, because that is what a replacement has to match.
8. Confirm the plinth height.150mm is conventional, and it is what makes a 720mm carcass reach 870mm before the worktop. If the legs have been wound up or down, the plinth may have been cut and the number will not be 150.

Tips

• Nominal and actual are not the same thing. A "600mm" base unit is usually a 600mm module including its share of the gap between units, and the carcass itself may be 596 or 597mm. Measure, do not calculate.
• If you are raising or lowering a worktop for comfort, the legs are the place to do it, and the plinth is cut to suit. Changing worktop height by more than about 50mm starts to affect appliance housings.
• European and British kitchens use the same 600mm module, but drawer front heights and door sizes differ. A German kitchen's doors will not fit a British carcass without checking the cup positions.

Common mistakes

• Ordering replacement doors from a published size chart — Manufacturers' door heights differ by a few millimetres, and the hinge cup position differs by more. Measure the door you have, including where the cups are, and order to those figures.
• Planning a 600mm gap for an appliance — A 600mm appliance in a 600mm gap does not go in. Appliance manufacturers publish a required aperture, which is usually a few millimetres larger, and it is the aperture figure you plan to.

Questions people ask