Monitor arm compatibility checker
Four things have to line up before an arm will hold your screen: weight, hole pattern, desk thickness and reach. Each one gets its own line below, with the number that decided it.
Waiting
—
Fill in your monitor and your arm to see whether they go together.
- On the arm—
- Screen to clamp—
- Back from the front edge—
Drag the screen around the desk. The dashed circle is how far the arm reaches from the clamp. Objects can be focused with the Tab key: arrow keys move the focused object, and the [ and ] keys turn it.
Your monitor
Take the stand off the figure. Spec sheets often print both, and the stand can be a third of the total.
Across the screen, bezel to bezel. This is what the plan draws.
Corner to corner, the number it was sold as. Some arms cap this as well as the weight.
Your arm
The bottom of the arm's weight range. A gas-spring arm will not hold a screen lighter than this.
The top of the range, from the arm's own spec sheet rather than the shop listing.
How far the arm pushes the screen away from the clamp at full stretch. Arms vary a lot, so use your own figure.
Leave this at 0 if the spec sheet does not give a screen size limit.
The arm carries this as well as the screen, so it comes off the weight you have left.
Your desk
Left to right on the plan.
Front to back. The top of the plan is the back edge.
Measure at the back edge where the mount goes, not in the middle. Some tops taper.
Where the mount goes along the back edge. A drawer runner or a leg often decides this.
The thinnest top the mount is rated for.
The thickest top it will close on. This is the number that stops most thick desks.
What this assumes
- Every limit here is your arm's, not ours. The weight range, the reach and the mount range come from the spec sheet you type in. The starting numbers match a common desk arm and are there to be replaced.
- The screen is drawn as a panel seen from above, 6 cm deep. That is about right for a flat monitor and its bracket. A curved screen takes a little more.
- Reach is measured to the middle of the screen's back. That is where the arm holds it, so turning the screen changes the distance. The dashed circle is drawn from the clamp.
- Twist is not calculated. A wide screen loads the joint harder than its weight suggests. Arms are not rated in twist, so there is nothing honest to compare against. The tool checks the arm's own screen size limit when you give it one.
- The clamp is drawn about 7 by 9 cm. Real mounts differ. It is there to show where the arm starts, not to check whether the mount clears a drawer.
How this calculation works
- Add up the load
- Match the hole pattern
- Measure the desk top
- Check reach on the plan
load on the arm = monitor weight without its stand + adapter plate weight
The four checks are independent. A screen can be well inside the weight range and still have the wrong hole pattern. An arm that suits the screen perfectly can be useless on a 70 mm worktop. So each one is answered on its own line, and the verdict at the top is only the worst of them.
Compatible means every line passed. Caution means something needs a look. A desk thinner than the mount asks for will do it, so will a wide screen on an arm that gives no size limit. Not compatible means a number is out of range, and the line says which one.
| Pattern | Screw spacing | Where it turns up |
|---|---|---|
| 75 × 75 | 75 mm across, 75 mm down | Smaller panels. Most desk arms take it. |
| 100 × 100 | 100 mm across, 100 mm down | The common one. Nearly every desk arm takes it. |
| 200 × 100 | 200 mm across, 100 mm down | Wider panels. Needs a plate on most desk arms. |
| 200 × 200 | 200 mm across, 200 mm down | Heavier panels and some TVs. Needs a plate. |
| 400 × 200 | 400 mm across, 200 mm down | TV territory. A desk arm will not take it directly. |
| 400 × 400 | 400 mm across, 400 mm down | TV territory, and usually beyond a desk arm's weight limit too. |
Where to find each number
| Number | Where it comes from |
|---|---|
| Monitor weight | The maker's spec page, under "without stand". The box weight is no use. |
| Hole pattern | Measured off the back of the screen with the stand removed. |
| Arm weight range | The arm's manual. Both ends of the range are printed. |
| Mount thickness range | The arm's manual, listed separately for the clamp and the bolt-through mount. |
| Desk thickness | Measured at the back edge with a ruler. |
Too light is a real failure
A gas-spring arm has a piston inside pushing up. You set the tension for the screen you are hanging, and the screen then stays wherever you leave it. There is a bottom to that adjustment. Hang a 2 kg portable screen on an arm built for 4 to 9 kg and it will creep upwards every time you push it down.
This catches people who buy a good arm for a light screen, thinking the extra capacity is spare. It is not spare. Check the bottom of the range as carefully as the top. The other way out is a bolt-tightened arm, which holds its position by friction and has no minimum.
The desk stops more arms than the monitor does
Most desk arms clamp tops up to about 60 mm. Plenty of solid wood tables are thicker than that. A top with a lip or a rounded underside can beat the clamp even when the middle measures thin enough. Measure at the back edge, where the jaw actually closes.
The bolt-through option puts the post through a hole in the desk. It has its own thickness range, and that range is rarely the same as the clamp's. Switch the mount type above and the tool reminds you to read the right one. If your desk has no hole, drilling one is a decision you cannot take back.
Reach is why the screen ends up too close
An arm's reach is the distance from the clamp to the mounting plate at full stretch. Drag the screen forward on the plan and watch the circle: once the back of the screen leaves it, the arm cannot get there. On a deep desk with the clamp at the back, that often means the screen sits closer to you than you wanted.
Two fixes. Move the clamp along the back edge to change the angle, which the plan will show you. Or accept the screen further back and drop the desk depth you actually use. An arm near full stretch also sags more than one working halfway out.
Common questions
How do I know which VESA pattern my monitor has?
Take the stand off and measure between the centres of the four screw holes on the back, across and down, in millimetres. Four holes 100 mm apart each way is a 100 by 100 pattern. Screen size does not tell you the pattern, because makers differ.
Can a monitor be too light for a monitor arm?
Yes, on a gas-spring arm. The spring pushes up with a set force, so a screen under the arm's minimum weight drifts back up after you move it. Most arms give a range such as 2 to 9 kg, and both ends of it matter.
Does a VESA adapter plate count towards the weight limit?
Yes. The arm carries the plate as well as the screen. Add the plate weight to the monitor weight, then compare the total with the arm's maximum. A steel plate is often around half a kilogram.
For the hole pattern on its own, and what to do when it does not match, read the VESA pattern guide. If the desk itself is the problem, the dining table room size calculator uses the same plan view for a whole room.
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