How to Measure for a Dishwasher: Cabinet Cutout Guide

Why measure the cutout before you shop

A dishwasher has to fit into the space under your countertop. The cabinet cutout is the opening between two cabinets or at the end of a cabinet run. Knowing its exact dimensions tells you which categories of dishwashers are realistic options and which ones you can rule out before you spend time comparing models.

ENERGY STAR groups dishwashers into two capacity classes: standard models hold at least 8 place settings plus 6 serving pieces, while compact models hold less than that. In practice, the width of the cutout is usually the main factor that decides which class fits: full-size openings typically accept standard models, while narrower openings require compact ones. The standard dishwasher dimensions article explains the trade-offs in more detail. If your cutout is on the narrow side, the best 18 inch built-in dishwashers guide is where to start.

How to measure the width

Width is the horizontal distance between the left and right cabinet walls where the dishwasher will sit. Use a tape measure. Press the hook against the left wall, extend the tape to the right wall, and read the measurement at the widest point. Take two or three readings: one near the front of the opening, one at the middle, and one near the back. Cabinet openings are not always perfectly square, and the narrowest point is the one that matters.

Write down the narrowest width you find. That number is the maximum opening you have for the dishwasher body, not counting the door, which fits over the front face of the cabinet. The spec sheet for any dishwasher lists the width of the unit itself, so match that against your narrowest opening. If the opening is roughly 24 inches, you are looking at a standard-size machine and the best 24 inch built-in dishwashers guide covers the field. If it is noticeably less, around 18 inches, the best 18 inch built-in dishwashers list is the right place to compare.

• Measure at the front, middle, and back of the opening.
• Use the narrowest width as your working number.
• Do not include trim or door frames in the measurement.
• If the opening has a slight taper, note how much narrower the back is than the front.

How to measure the height

Height is the vertical distance from the finished floor up to the underside of the countertop. If your countertop overhangs the opening, measure from the floor to the bottom edge of that overhang, not to the top of the counter. Use a tape measure held vertically. Place the end on the floor, extend it up, and read the point where it touches the countertop underside. Again, take two readings: one at the front edge of the opening and one at the back, because floors are not always level.

The shorter of those two readings is the maximum height you have to work with. A dishwasher sits on its own adjustable feet, and the spec sheet lists both the minimum and maximum installed height for each model. As long as your cutout height falls within that range, the unit can be leveled to fit. The process here is the same step you will repeat when the unit arrives. If your opening is unusually low, the low profile dishwashers article explains what your options are.

• Measure at the front and at the back of the opening.
• Use the shorter reading as your maximum height.
• Check that the floor is level across the width of the opening.
• If the countertop overhangs, measure to the underside of that overhang.

How to measure the depth

Depth is the horizontal distance from the front face of the cabinet or the front edge of the opening straight back to the rear wall. This measurement tells you whether the dishwasher body and its rear connections will clear the wall and any plumbing that runs behind the space. Use the tape measure and extend it from the front edge of the opening back to the wall. Record the distance.

Most built-in dishwashers need to sit fully inside the cabinet opening, with enough room behind them for the water inlet hose, the drain hose, and the electrical cord. The spec sheet lists the depth of the unit, but that number usually excludes the fittings that protrude from the back. Add some allowance for those connections when you compare the depth against your cutout. If your opening is shallow and space is tight, the portable vs drawer dishwashers comparison can help you decide whether an alternative format avoids the depth problem entirely. For drawer models, see the best drawer dishwashers guide. For a conventional built-in, compare the depth and the rest of the spec sheet from the maker's page.

Connections and clearances to check at the same time

While you have the tape measure out, note where the utility connections are located. The water supply line and the drain hose usually enter the opening through a hole in the back wall or the floor. The electrical connection can be a cord with a plug or a hardwired line. Record the position of each one: how far from the side walls and how far above the floor. This matters because the dishwasher has to reach all three connections, and the hoses have limited length.

Also check the floor under the opening for level. A dishwasher is leveled with its adjustable feet, but if the floor slopes noticeably, the install instructions may call for shimming. Check the opening for any obstructions: a gas line, a water pipe, or an electrical cable that sticks into the space will reduce the usable width or depth.

Before you order, verify that the space between the top of the dishwasher and the underside of the countertop matches the clearance listed in the installation instructions. Most units list a minimum gap at the top to allow the door hinge to work properly. The dishwasher installation clearances article goes into the fine points of what needs to line up.

Match the measurements to the model spec sheet

Once you have the three dimensions and the connection locations, you can compare them against the spec sheet of any dishwasher you are considering. Every maker publishes the width, height, depth, and installation clearances for each model. Look at those numbers, not the marketing copy. A model is only a fit if the width of the unit is less than your narrowest width, the adjustable height range covers your measured height, and the depth, including rear connections, fits within your measured depth.

If your numbers line up with a standard full-size opening, the best 24 inch dishwashers guide is the comprehensive comparison. If the width or height is more constrained, the best 18 inch built-in dishwashers guide focuses on the models that fit. For a compact format that does not need a full-size cutout at all, the best countertop dishwashers guide covers units that sit on the counter rather than inside the cabinet. And for homes where a cabinet under the counter is not available, the best portable dishwashers guide explains what a rolling unit requires in terms of faucet and drain access.

What to pick based on your cutout

Questions

What if my cabinet opening is slightly narrower than the listed width of the dishwasher?

It will not fit. The listed width is the minimum opening required, and the unit needs a small clearance on each side. If your opening is narrower than the spec sheet width, you need a model with a smaller width, which usually means a compact 18-inch class unit. Compare the rough-in dimensions on the spec sheet against your narrowest width before you buy.

Should I measure to the floor or to the top of the finished flooring?

Measure to the top of the finished flooring that is actually installed. If you plan to install new flooring after the dishwasher, account for its thickness. The height measurement needs to reflect the finished surface the unit will sit on when it is in use.

How much clearance do I need behind the dishwasher for the hoses and cord?

The spec sheet lists the depth of the unit, but that number usually does not include the fittings at the back. You need extra depth behind the unit for the inlet hose, drain hose, and electrical cord. A common rule is to add a few inches to the unit depth to get the minimum opening depth. Measure your cutout depth before you compare.

Can I install an 18-inch dishwasher in a 24-inch opening?

Technically yes, because the unit is narrower than the opening, but the gap on each side will be visible and the front panel will not fill the cutout. You would need filler strips to close the gap. Most installations pair an 18-inch unit with an 18-inch opening. If you have a 24-inch opening, a standard 24-inch unit is the cleaner fit.

Do I need to measure the depth with the door open?

For the cabinet cutout, no. The cutout depth is measured with the door closed, from the front of the opening to the back wall. The door open depth is a separate measurement that matters for clearance in front of the unit, so you can open the door fully and pull out the racks. That is a different number from the cutout depth.

What if my floor is not level under the cutout?

Dishwashers have adjustable feet at each corner, so a small slope can be corrected. Note the height difference between the front and back of the opening. If the slope is large, the unit may not level out within the range of its feet, and you may need to shim under the low side. Check the installation instructions for the maximum allowable slope.