A sliding tray needs to match both the footprint of the appliance and the depth of the cabinet space above it. Measure the appliance's base at its widest point, add roughly an inch of clearance on each side, then check that the combined height of the appliance plus the tray still clears the cabinet. Getting this wrong is the most common reason a tray gets returned.
Why the Wrong Measurement Is So Easy to Make
Most people measure the appliance and stop there. The tray needs to hold the appliance, so the appliance's dimensions feel like the whole answer. They're only part of it. A tray that fits the base perfectly but adds three-quarters of an inch to the total height can turn out to be the reason a coffee maker no longer slides under the cabinet at all.
Step One: Measure the Base, Not the Body
Appliances flare out as they go up. A coffee maker's reservoir might be wider than its base, and a stand mixer's bowl often overhangs the footprint it sits on. What matters for a sliding tray is the base, the part that makes contact with the counter, since that's what the tray needs to support.
Measure the base at its widest point in both directions. Write both numbers down before doing anything else.
Step Two: Add Clearance
A tray that matches the appliance's base exactly leaves no margin for placing it slightly off-centre, and no room for a cord to sit flush against the side. Add about an inch to each dimension as a rule of thumb. For a coffee maker with a 10-inch by 6-inch base, that means looking for a tray in the 12-inch by 8-inch range rather than hunting for an exact match.
Too much clearance causes its own problem: an appliance that shifts around on a tray that's meaningfully larger than it needs to be. The goal is a comfortable margin rather than a spare few inches on every side.
Step Three: Check the Combined Height
This is the step most people skip, and it's the one that causes returns most often. A sliding tray adds height under the appliance, typically under an inch, but under an inch is still enough to matter if the appliance is already snug beneath a cabinet.
Measure the clearance between the counter and the bottom of the cabinet above it. Then measure the appliance's own height. If the appliance already uses most of that clearance, check the tray's exact height before buying rather than assuming it'll fit. A tray listed at 0.85 inches tall needs exactly that much spare room.
What to Do If the Numbers Are Tight
If the combined height comes within a quarter inch of the available clearance, it's worth measuring twice from different points on the cabinet, since cabinets aren't always perfectly level, and checking whether the appliance's feet or base has any give that a slightly taller tray might absorb.
If there's genuinely no room to spare, a lower-profile tray is the right fix rather than forcing a taller one to work. Trays vary in height by design, and the flattest options exist specifically for this scenario.
Multiple Appliances, One Tray
Some kitchens want a single tray to serve a rotation of appliances rather than one dedicated to a single coffee maker. In that case, measure the largest appliance in the rotation and use those dimensions as the baseline. A tray sized for the biggest piece in the group will comfortably hold anything smaller, with the same one-inch clearance rule applied to the largest base.
A Five-Minute Check Before You Buy
Base width, base depth, one inch of clearance on each side, and the combined height against available cabinet clearance. Four numbers, five minutes with a tape measure, and the tray that arrives is the tray that works, rather than one that has to go back.