VESA patterns, and what to do about a mismatch
On the back of most monitors are four screw holes, set out in a square or a rectangle. The gap between them, in millimetres, is the pattern. VESA is the trade body that publishes the flat display mounting standard these patterns come from, which is why people call them VESA holes.
A monitor arm has a plate with holes to match. When the two agree, the screen bolts straight on. When they do not, you need a plate in between, or a different arm.
Measure your own
Take the stand off first. Some stands sit over the holes.
Measure from the centre of one hole to the centre of the next, not from edge to edge. Left to right is the first number. Top to bottom is the second. So four holes 100 mm apart each way is 100 × 100.
Real patterns land on round numbers. If your tape says 98 mm, you have 100 × 100 and a slightly bent tape.
Two holes, or four holes in a diamond, is not a VESA mount.
The patterns you will meet
| Pattern | What it turns up on |
|---|---|
| 75 × 75 | Small panels. Most desk arms take it. |
| 100 × 100 | The common one. Nearly every desk arm takes it. |
| 200 × 100 | Wider panels. Needs a plate on most desk arms. |
| 200 × 200 | Heavier panels and small TVs. Needs a plate. |
| 400 × 200 | TVs. A desk arm will not take it directly. |
| 400 × 400 | TVs, and past what a desk arm can hold anyway. |
Desk arms are built around the two small patterns. Once you are into 200 mm spacings you are looking at a wall mount, a heavy-duty arm, or a plate.
Screen size tells you nothing
There is no rule that turns inches into a pattern. Two 27 inch monitors from two makers can have two different patterns. A light 32 inch screen can be 100 × 100 while a heavy 27 inch one is 200 × 100.
Anyone who tells you a size always means a pattern is guessing. Measure the back of your own screen.
When there are no holes at all
Some monitors have none. The back is curved, or the stand bolts into a fitting that only that stand matches. This is common on cheap screens and on all-in-one machines.
Two ways out. The maker may sell a bracket for that exact model, which is the tidy answer. Or a third-party bracket grips the panel by its edges and carries a VESA plate of its own. Those work, but they hide part of the bezel and they add weight the arm has to carry.
Adapter plates
An adapter plate is a piece of steel with two sets of holes. Your monitor’s pattern goes on one side. The arm’s pattern goes on the other.
Check three things before you buy one.
Both sides have to match. A plate sold as “200 × 100 to 100 × 100” is no use if your screen is 200 × 200. The listing has to name your pattern, not a pattern near it.
The weight counts. The arm holds the plate as well as the screen. A steel plate is often around half a kilogram, which comes straight off the weight you have left. On an arm that was already close to its limit, the plate is what pushes it over.
It holds the screen a little further out. Only a few millimetres, but it adds to the load on the joint. On a heavy screen near the arm’s maximum, that is worth knowing about.
Screws are the other half of the job
The bag of screws that comes with an arm is a mixed bag, and the right one for your screen may not be in it.
Screws that are too long bottom out inside the monitor before they pull anything tight, so the screen feels solid and is not. Screws that are too short strip the thread. Monitor makers usually print the thread size and how deep the hole goes on the same page as the pattern. Look it up, and buy the screw if you have to.
Curved backs sometimes need spacers so the plate sits flat. Arms that need them ship with them. If yours did not and the plate rocks, stop and find spacers rather than pulling the screws down hard.
The pattern is one check of four
A matching pattern does not mean the arm will work. It also has to hold the weight of your screen. It has to fit the thickness of your desk top. And it has to reach far enough to put the screen where you want it. Any one of those can rule out an arm that bolts on perfectly.
Put your numbers into the monitor arm compatibility checker. It answers all four on separate lines, so you can see which one is the problem.