What Are Grommet Holes Used For In a Computer Desk?

This is surprisingly one of the most common questions we get from readers—particularly with regards to standing desks—but the same information applies for all kinds of desks and even standing desk converters and treadmill desks. So let’s dive in, shall we?

Grommet was of course Wallace’s endearing sidekick in the iconic British Claymation series of Wallace And Grommet. But today we’re talking about the other kind of grommet, the kind you’ll find cut into your tabletop for passing through cables or installing power modules. In this article we’re going to discuss what these grommet holes are for, what standard sizes they come in, what kinds of covers are used to cap them, desktop power management accessories you can slip into them, and even what kinds of colors and finishes are available to accentuate your workstation.

The technical definition of a tabletop grommet is simply a hole in your tabletop (or two, or sometimes even three) through which you can pass cables. These might include power cords, monitor cables, USB devices, printer cables or any other cables that needs to go from a device on top of your desk down to a cable trough, computer, office treadmill, power strip, or wall outlet underneath the desk. These covers, caps, or rings are typically made of plastic or rubber to protect cables from getting cut by a sharp edge. They are cheap, come in a million sizes and designs, and are sometimes supplied with the desk. If not, you can find a plethora of grommet covers on Amazon.

There are also some pretty cool options these days for grommet-mounted power modules that bring nice clean outlets up to the tabletop where you can plug in your phone, tablet, laptop, and other devices without having to bend over underneath your desk each time. These grommet-mounted devices come in a few standard sizes so you want to make sure that the device you buy is the correct diameter for the grommet hole(s) in your tabletop.

Although less common these days, in the early days of the desktop computer industry a lot of monitor arms were designed to be installed in those grommet holes in the desktop. This is really a thing of the past since 98% of monitor arms these days are edge-clamped to the desk, but you still see a lot of ergonomic monitor arms that come with parts for alternative grommet hole mounting.

The Many Kinds of Grommets

The term “grommet” really refers to a snap-in grommet cover or ring. These serve several functions. On the vast majority of desks the grommet hole exposes raw wood inside the tabletop’s core—typically made from particleboard or MDF, or solid wood on fancier desks—which can be both visually offensive and create a risk to the integrity of the top should a liquid be spilled into them. So the first function of a grommet cover is to conceal that ugly raw wood and protect it somewhat from spills.

Plastic grommet covers don’t to anything to protect the exposed wood from the long-term ravages of humidity and temperature changes, so they are really sort of a first line of defense.

Higher quality tabletops will have completely finished and sealed grommet holes, which are pretty to look at and offer a far greater degree of protection from spills. This is especially true of 3D-laminated tabletops, which create a hermetic seal over the full depth of the grommet hole, and can give the entire tabletop the look of hand-carved natural hardwood.

As for really high-end solid wood tabletops like iMovR makes, the holes are beautifully sanded, stained, and sealed.

The last thing you’d want to do is cover these grommet holes because they’re actually much prettier to look at than plastic caps. These 80mm holes accept a wide selection of power management devices as well, if that is what you want to use them for.

What Size Grommet Hole(s) Do You Need?

Most desk makers don’t give you any options around the diameter of their grommet holes. If you’re lucky, they might make them an optional selection for the desktop, but the diameters and locations of the grommet holes are usually set in stone.

If you need something even more custom you can always buy a standalone desktop and the desk base separately, and then cut your own grommet holes out. This is a more practical approach, for example, if you’re looking to insert a large rectangular power module into a conference table top.

But for standard situations, the most important thing is to ensure that the grommet’s diameter can accommodate all the cables you plan to run through it. Or, if you plan to add in-grommet power modules, that the diameters will match.

To find out exactly which size grommet you’ll need for cable pass-through, loosely bundle all the cables you’ll be working with in one hand, and then break out a ruler or tape measure. Measure across the cable bundle’s widest point; this dimension is the minimum grommet diameter that will work for your application. However, cables always perform better with room to breathe, so always size up a little bit. Giving your cables a roomier space to pass through will prevent signal attenuation, make the cables easier to route in different directions on your desktop, and can even give you some leeway for future additions.

Most standing desks, for example, come with either 1.75″, 2″, 2-3/8″ or 3″ grommet holes, but there are wild variations to this so always check the specs before you buy. In some cases, the diameters are metric, the three most common being 50mm (2″), 60mm (2.36″) and 80mm (3.15″). The smaller 2″ holes were more popular when installing monitor arms through the desktop was still a thing. Nowadays larger holes like 3″ or 80mm are coveted because they can accept much more robust grommet-mounted power modules like the Rondo, Spectra, and Dyna. If you want to bring AC power, USB ports, and even wireless charging up to the desktop, 3″ or 80mm (3.15″) is the way to go these days.

Brands like Jarvis tend to have 3″ grommet holes on their desks. iMovR and Uplift have 80mm holes on most of their desks. Meanwhile, a lot of Chinese brands like Autonomous can have non-standard hole sizes, like the 2.4″ holes on their SmartDesk Core. Some brands, like Vari, don’t offer any grommet holes anymore (cutting every penny of cost), so for power modules you’re going to be limited to those that can be edge-clamped.

Where Should Grommet Holes Be Located In The Desktop?

This is highly variable, but the most popular brands of standing desks usually put dual grommet holes within a few inches of the back edge of the desktop and anywhere from 7″ to 13″ from the left and right edges of the desktop, depending on the size of the given desk. In this example from the Lander Desk specifications you can see fairly typical grommet hole placements.

Some desks have a grommet hole just in the center of the desktop, 2″-3″ off the back edge. This harks back to the days when monitor arms would often be installed in a grommet hole, as discussed above. The biggest downside of using grommet-mounted monitor arms on a standing desk is that arcing path of the arm causes the monitor to be frustratingly off-center. Even if you manage to get your monitor centered when sitting, as soon as you stand and your lower spine straightens out—meaning that you actually need a few more inches of monitor height relative to keyboard height—the arcing motion of the arm will move your display off-center (Learn more about this in our ergonomics primer on adjustable monitor arms).

We’ve even seen some desks that have one grommet hole in an odd position that isn’t centered, and this is usually because there is a desk frame member interfering with placing it in the center. This is found on the Effydesk Wildwood standing desk, for example.

Standing desk converters often also have grommet holes, albeit smaller ones in proportion to the small worksurfaces on a converter. Most converter models have a single grommet hole, covered with a black plastic cap, centered along the back edge of the top worksurface.

The most extreme example we’ve found in lab testing many dozens of models is the Versadesk Power Pro, which has three small grommet holes they promote for monitor arm installation or cable pass-thru. And that’s fine if all you’re planning to use is a fixed-height monitor mount, but if installing an adjustable ergonomic monitor arm you’ll wind up with the same problem as noted above.

To the degree that some desk makers include grommet hole covers as standard or optional add-ons, they are usually either black or white in color. This is one of those small accent opportunities that, if you’re compelled to, can allow you to express your design style a little bit by replacing those black caps with something more colorful.

There are many options on Amazon, though you’ll have to scroll through a lot of white and black products to find them. For example there are these zinc alloy grommet covers in metallic finishes or these brown grommet caps that might blend in better with certain woods. One standing desk maker, iMovR, takes color selections of grommet-mounted power modules and cable pass-through covers seriously. While they offer alternative finishes on several of their desktop power management devices, they offer even more stylistic choices on their made-to-order designer standing desks. A whopping 11 pastel colors plus 6 metallic finishes are offered in their Rondo Micro grommet insert line to match up with the 17 stains that they offer on their birch Captain’s and Ensign’s designer standing desk lines.