Appliance openings: the sizes your cabinets have to hit
The cabinet grid did not come first. Appliances did, and the whole standard kitchen is arranged so that machines built by other companies slide into it. That makes appliance openings the least negotiable dimensions in the room, and the ones most often got wrong, because the number that matters is in the installation manual rather than on the box. This page covers what each appliance needs, what is fixed and what is not, and the four things to look up before you draw anything.
A dishwasher fixes your counter height, because it is built for an opening about 34½" (876 mm) tall and that is exactly what a base cabinet gives it. An oven fixes nothing, because every model has a different cut-out, which is why oven cabinets are shipped with an undersized niche and trimmed on site. A refrigerator needs clearance you cannot see on a drawing. Above a cooktop, one number is building code rather than preference. Read the manuals, then draw.
Why the grid exists at all
Nothing in law says a kitchen base cabinet is 34½" tall. The cabinet standard is a performance standard and says so itself: it tests how a cabinet survives, not what size it is. So the grid is a market convention, and what holds it in place is that a dishwasher and an under-counter oven are manufactured to fit it.
That is a stronger force than a rule. Break the convention and nothing is illegal; you simply lose compatibility with machines you did not make and will replace three times over the life of the kitchen. Which is the real reason to be careful about lowering a run for a shorter cook, and the reason the guide to counter height keeps pointing at the legs rather than the carcass.
What each appliance actually needs
Appliance
The opening
What is fixed
What to check
Dishwasher
Roughly 24" wide × 24" deep × 34½" (876 mm) tall
The height, which is why base cabinets are 34½" and why counter height barely moves
Panel-ready models need extra depth for the door and the panel. Compact models exist at 18" wide
Built-in oven
The cut-out in the manual, not the oven's outside size
Nothing. Cut-outs vary by model, which is why cabinets ship undersized and get trimmed
Cut-out height, depth behind, and the ventilation gap the maker specifies. Also the weight
Refrigerator
Its own footprint plus clearance on the sides, back and top
Nothing, and the range of sizes is enormous
Door swing and hinge side, the depth of the handle, and whether it is counter-depth or standard
Microwave
Varies. Over-range, built-in and drawer models are three different problems
Its floor no higher than 54" (1372 mm) off the ground, for safety rather than fit
Trim kits, which change the opening entirely, and ventilation
Range hood
Width to suit the cooktop, and a mounting height from the maker
30" (762 mm) from the cooking surface to unprotected combustible material, by code
Ducting route and the chimney height if it is a chimney model
The oven niche, and why it arrives too small
This is the detail that catches out homeowners and occasionally fitters, and almost nobody explains it.
Buy an oven housing cabinet from a catalogue and the niche in it will be smaller than any oven you might buy. Different manufacturers ship different sizes, and none of them are the size of your oven. That is deliberate. The cabinet is made undersized on purpose, and the fitter cuts the opening up to the cut-out dimension in your appliance manual on the day.
The reason is that a cut-out can be enlarged and cannot be shrunk. If the factory built the niche to suit a 30" oven and your oven needs slightly less, you would have a gap you cannot close. Built small, one pass with a saw fits it to anything within range.
Our own oven cabinet is modelled in the trimmedstate, with the niche already at the size a typical 30" oven wants, because a designer needs to see the finished result rather than the blank. It is worth knowing that the physical cabinet you receive from any maker is a stage behind that drawing.
What that means for you in practice: choose the oven before the kitchen is built, or at least know its cut-out. Real ones in the same 30" class differ by more than half an inch, which is the difference between a cabinet that fits and a cabinet that has to be rebuilt.
The dishwasher, which decides more than it should
A standard dishwasher is roughly 24" wide, 24" deep and needs an opening about 34½" tall. Those three numbers are why the base cabinet grid looks the way it does, and why the guide to standard dimensions calls the dishwasher the thing that holds the whole vertical stack in place.
Three things people miss:
The opening has no cabinet in it. A dishwasher sits in a gap between two cabinets, under the worktop, fixed to the underside of it or to the neighbours. Nothing is built around it.
A panel-ready machine needs more room. The door carries a cabinet front, which adds thickness in front and sometimes demands a specific hinge and rail. Decide on that before the run is drawn.
Where it sits matters as much as whether it fits. The guideline is within 36" of the sink edge, and the door drops forward into the aisle, so a dishwasher opposite an island can block the room while it is open.
The refrigerator and the cabinet above it
Fridges vary more than any other appliance in a kitchen, and the drawing usually shows a rectangle where the real thing needs air. Check three clearances in the manual: at the sides, behind and above. A fridge in a tight enclosure runs hot, works harder and dies sooner.
Two design details that follow from the fridge rather than from taste:
The cabinet above it is deep, not shallow.Wall cabinets are usually 12" deep, and the one over a refrigerator goes to 24" to match the appliance. Otherwise a foot of dead space sits on top of the fridge, gathering dust and reachable from nowhere. These come in a ladder of short heights, from 12 up to 24", to fill whatever gap is left up to the ceiling.
Counter-depth is a different appliance. A counter-depth fridge lines up with the run and holds less. A standard one projects several inches into the room and changes how the whole wall reads. Decide which before the layout, since it moves the walkway.
And check the handle side. A fridge door that opens into the working aisle instead of away from it is a daily annoyance that costs nothing to avoid on paper, and the guideline asks for landing space on the handle side so you can put shopping down with the door open.
Above the cooktop: the one number that is law
Everything else on this page is convention or manufacturer specification. This is building code: 30" (762 mm) between a cooking surface and an unprotected combustible surface above it. A wooden or board cabinet is combustible.
That single requirement is why a standard run puts a short cabinet over the range instead of a full-height one, and why the wall cabinet heights ladder includes an 18" box that exists mainly for this position.
Appliances change the picture rather than the rule. A range hood or an over-the-range microwave is a listed appliance with its own tested mounting height, commonly somewhere between 24 and 30" above the cooktop depending on the model and whether the range is gas or electric. Follow that manual. The short version: furniture above burners obeys code, appliances obey their instructions.The gap guide covers what that does to the rest of the elevation.
Four things to look up before you draw
The cut-out, not the product size.For anything built in, the manual gives an opening dimension that is not the same as the appliance's own width and height. That is the number the cabinet is built to.
Clearances for air. Ovens, fridges, microwaves and dishwashers all specify gaps for ventilation. They are not optional and they are invisible on a plan.
Doors and their swing. Which way, how far, and what they hit. An oven door dropping open in front of an island aisle is a planning mistake, not an installation one.
Services. Water, waste, gas and power have to arrive where the appliance is, and moving them later is the expensive part of any kitchen.
Doing this before the drawing is finished costs an evening. Doing it afterwards costs a cabinet, and sometimes a worktop.
Draw the gap the appliance needs
Set your own dimensions on the cabinets either side of an appliance and the run rebuilds around the opening, so the gap you leave is the gap the manual asked for. Check it against the layout before anything is cut, while a mistake still costs nothing.
A standard dishwasher wants an opening roughly 24 inches wide, 24 inches deep and about 34½ inches (876 mm) tall, which is exactly what a standard base cabinet run provides. Nothing is built into that gap: the machine sits between two cabinets under the worktop. Two things catch people out. A panel-ready model, where the door carries a cabinet front, needs extra depth and sometimes specific hardware, so decide on that before the run is drawn. And compact 18 inch wide machines exist, which are the answer when the layout genuinely cannot spare 24 inches.
Why is an oven cabinet niche smaller than the oven?
On purpose. Oven cut-outs differ between manufacturers and even between models in the same size class, so cabinets are built with an undersized niche and the opening is cut to your appliance's stated cut-out on site. The logic is that an opening can be enlarged and cannot be shrunk: build it to suit one oven and a slightly smaller appliance leaves a gap you cannot close. It also means you should choose the oven before the kitchen is built, or at least know its cut-out, because real ovens in the same 30 inch class differ by more than half an inch.
How much clearance does a refrigerator need?
Check the manual for three separate figures: at the sides, behind and above. Fridges vary far more than other appliances and a machine in a tight enclosure runs hot, works harder and fails sooner, which is a slow expensive way to save an inch. Also decide early between counter-depth and standard depth, because a standard fridge projects several inches past a 24 inch run and changes the walkway, and check the hinge side so the door does not open into the working aisle. Guidelines ask for landing space on the handle side so you can put shopping down with the door open.
What size cabinet goes above a refrigerator?
A deep one. Wall cabinets are normally 12 inches deep, but the cabinet over a refrigerator goes to 24 inches to match the appliance below it, otherwise a foot of dead space sits on top of the fridge collecting dust and reachable from neither side. Height is chosen to fill whatever is left up to the ceiling, from a ladder of short boxes running 12, 15, 18, 21 and 24 inches. An 18 inch box at 24 inches deep is the most common combination.
How high above a cooktop can a cabinet be?
Building code requires 30 inches (762 mm) between the cooking surface and an unprotected combustible surface above it, and a board or wooden cabinet is combustible. That is why a standard kitchen puts a short cabinet, typically 18 inches tall, over the range rather than a full 30 inch one. If what sits above the burners is a listed appliance instead, such as a range hood or an over-the-range microwave, follow that appliance's installation instructions, which commonly specify somewhere between 24 and 30 inches depending on the model and the fuel. Furniture obeys code, appliances obey their manuals.
How high should a microwave be mounted?
Whatever the model allows, with one guideline worth treating as firm: the floor of the microwave should be no higher than about 54 inches (1372 mm) off the ground. That is about safety rather than fit, because you take a container of boiling liquid out of a microwave with your arms extended, and above shoulder height you cannot see into it or control the tilt. Beyond that, over-range, built-in and drawer microwaves are three different installation problems, and built-in models usually need a trim kit that changes the opening entirely.
What should I check in an appliance manual before designing a kitchen?
Four things. The cut-out dimension, which is the opening the cabinet is built to and is not the same as the appliance's own size. The ventilation clearances at the sides, back and top, which are invisible on a plan and not optional. The doors, meaning which way they swing, how far they project and what they hit when open. And the services, since water, waste, gas and power have to arrive where the appliance is, and moving them later is the expensive part of any kitchen. An evening spent on this before the drawing is finished saves a cabinet afterwards.
