Choosing a monitor arm mounting size means matching several measurements, not just finding a plate that looks about right. Check your monitor’s VESA pattern and weight, then measure the desk and the space where the arm must move.
1. Identify the mounting pattern on your monitor
Most monitor arms attach to a standardized pattern of threaded holes on the back of a display. The common patterns are 75 × 75 mm and 100 × 100 mm. The first number is the horizontal distance between hole centers; the second is the vertical distance.
Find the pattern
Look for a recessed square or rectangular area around four threaded holes on the rear of the monitor. Measure from the center of one hole to the center of the neighboring hole, horizontally and vertically. A ruler marked in millimeters is useful; if you measure in inches, convert carefully (1 inch equals 25.4 mm). Measuring between hole edges instead of centers can give a misleading result.
The monitor’s manual or manufacturer product page may list a VESA mounting pattern. Check the exact model number, including any suffix: two versions of a display family can have different backs or mounting provisions. If the holes are hidden behind a removable stand cover, follow the monitor instructions for removing it. Do not force a cover or remove screws that appear to hold the display casing together.
| What to check | Where to find it | Why it matters |
|---|---|---|
| VESA pattern | Manual, specifications, or hole-center measurement | The arm plate must match or explicitly support it |
| Display weight | Manufacturer specifications, excluding the stand if stated | The arm must support the monitor within its rated range |
| Desk thickness | Measure at the mounting edge or grommet | The clamp or bolt must fit and tighten securely |
| Base clearance | Measure the desk edge, wall, and nearby objects | The arm needs room to attach and move |
If there are no VESA holes
Some displays use a proprietary mount, a stand that cannot be removed, or no standard mounting interface. A model-specific VESA adapter may be available, but compatibility depends on the monitor’s shape, attachment points, and weight. Verify that the adapter is approved for the exact display and that it attaches as its instructions require. A generic adapter that grips the bezel can cover vents, press on the screen, or fail to hold securely.
If no suitable adapter is specified, keep the original stand or choose a different display. Do not drill the monitor casing or improvise a load-bearing attachment.
2. Match the arm’s plate and weight range
An arm’s mounting plate should fit the monitor pattern directly or include a clearly specified adapter. A plate with multiple slots may support more than one pattern, but do not assume that it covers every VESA size. Read the arm’s compatibility list and installation guide.
Next, compare the monitor’s weight with the arm’s supported range. Use the monitor’s weight without its original stand when the manufacturer provides that figure, because the arm supports the display itself rather than the removed base. If only a weight including the stand is available, look for a separate specification or ask the monitor maker; subtracting a guessed stand weight is unreliable.
The rated range matters in both directions. A display that exceeds the maximum can overload the mechanism or attachment. A display that is too light for a spring arm may rise on its own or be hard to position. Some arms use tension adjustment, while others have a fixed range. Confirm that your display falls inside the stated range and that the adjustment procedure applies to your arm type.
Account for the full mounted setup
A monitor may use a VESA adapter, spacer, or other accessory that adds weight or changes clearance. Include manufacturer-approved accessories in your fit check. A webcam or light mounted on the display can also affect balance, even if it does not change the VESA pattern. Check the arm maker’s guidance for accessories and permitted load; do not assume the advertised maximum leaves extra capacity for add-ons.
3. Measure the desk before choosing a base
The arm attaches to the desk with a clamp, a grommet bolt through an existing hole, or a fixed installation. Each method has different fit requirements. Measure the desk at the intended location rather than relying on a nominal desk thickness from a listing.
For a clamp, measure the desktop thickness where the jaws will sit and check the clamp’s specified minimum and maximum. Look underneath for a frame rail, drawer, cable tray, crossbar, or reinforcement that could block the lower jaw or tightening handle. Also check whether the desktop has a bevel, rounded edge, or lip that leaves too little flat contact area.
For a grommet mount, check whether the desk already has a suitable through-hole. Measure its diameter and note the desk thickness and underside clearance. Compare those dimensions with the arm’s bolt and hardware instructions. A cable-management hole may be too large, positioned poorly, or blocked by a reinforcing panel. Do not enlarge or drill a desk unless the furniture maker permits it and you understand the construction underneath.
A clamp that reaches the edge is not necessarily a good fit. The top and lower pads need stable contact, and the desk must be able to withstand the clamping force. Follow the desk and arm manufacturers’ instructions, including any limits for glass, hollow-core, composite, or unusually thin tops. If the instructions exclude your desk material or construction, use an approved mounting method or retain the monitor stand.
4. Check the arm’s reach and movement envelope
A correctly sized mounting plate can still leave the monitor in the wrong place. Consider the arm’s horizontal reach, vertical travel, tilt range, and the area the joints need to sweep through. Product specifications may describe reach from the post, base, or another reference point, so consult the drawing rather than treating one number as the distance from the desk edge to the screen.
Measure where you want the display’s center to sit, then account for the monitor’s width and the VESA point’s position on its back. A large display with a centered plate may extend well beyond the arm’s reach; an offset VESA mount can shift the screen relative to the arm. Check the maker’s drawings for supported screen sizes and movement limits as well as weight.
Also map the movement path. The rear of the screen, arm joints, cables, and base can collide with a wall, shelf, window frame, or a second monitor. A low desk shelf may prevent the arm from lowering far enough. A thick desktop may raise the mounting point and make it harder to position the screen at the height you want. Leave space for the arm to move without pinching cables or striking nearby objects.
For a dual-monitor setup, check the combined arrangement rather than assuming that two single arms will fit. Consider the width and weight of each display, the location of each VESA point, the shared base’s load limit, and the available desk span. A pole-mounted dual arm may place screens at different heights or restrict independent movement. Confirm the exact configuration is supported by the manufacturer.
5. Select the right mounting hardware and installation approach
Before ordering, compare the specifications as a complete set:
- VESA pattern or approved adapter compatibility
- Monitor weight range and any stated screen-size limits
- Desk-thickness range for the clamp or grommet hardware
- Required clearance under and behind the desk
- Arm reach, vertical travel, and movement limits
- Any restrictions for desk material, edge shape, or mounting location
Check what the package includes. The arm may have screws in several lengths or spacers for different monitor recesses. Use the fasteners specified for the display and arm. A screw that is too long may damage the monitor internally; one that is too short may not engage sufficiently. If the supplied screws do not fit, consult both manufacturers’ instructions for the correct size and permitted engagement. Do not force a screw into a threaded hole.
Install the base on a clear, stable section of desk and tighten it as instructed. Attach the arm and monitor in the sequence specified by the makers; some spring arms need to be held or secured during attachment. Support the display with another person if it is large or awkward to handle. Keep fingers clear of joints and do not let the arm snap open or retract uncontrolled.
After mounting, adjust the arm’s tension or balance only as described in its manual. Route cables with enough slack for the full range of movement, but keep them away from pinch points. Move the monitor slowly through its intended positions and check that the clamp stays seated, screws remain secure, and the screen does not drift or collide with anything.
6. Troubleshoot common fit problems
The mounting holes do not line up
Recheck the hole-center measurements and the monitor model. Confirm that the arm plate is oriented correctly and that any adapter is installed in the required direction. Some plates have movable or removable brackets, but use those features only as described in the arm instructions. If the pattern differs, get a compatible adapter or a different arm; do not force misaligned screws.
The monitor tilts down or the arm will not stay put
First verify the monitor’s supported weight, including any attached accessories, and confirm that the arm is designed for that load. If it is within range, follow the manual’s tension-adjustment steps. Adjust gradually while supporting the monitor. If the arm still drifts, check that the correct joint is being adjusted and that the mount is assembled as specified. Do not compensate for an incompatible load by overtightening a joint.
The clamp will not fit or the base feels unstable
Check the desktop thickness, edge profile, and underside obstructions against the clamp dimensions. Make sure the clamp pads have full, flat contact and that the hardware is assembled in the correct order. If the desk surface flexes, chips, or appears damaged, stop and remove the load safely. Use a mounting method approved for that desk or return to the original stand. A reinforcement plate may spread force on some desk types, but it must be suitable for the desk and permitted by the mount maker.
The screen sits too high, too low, or too far from you
The issue may be arm travel or geometry rather than VESA size. Compare the desired position with the arm’s movement diagram and the monitor’s VESA-point location. A different arm configuration or desk location may solve it. If the arm cannot reach the desired position without hitting a wall or desk feature, choose a model with suitable reach and travel instead of forcing the joints past their stops.
7. Know when an arm is the wrong solution
A monitor arm is useful when its mounting hardware fits, the desk can support the attachment, and the arm can move through the needed range. It is not automatically suitable for every display or workstation. A heavy screen, curved or unusually deep rear housing, proprietary stand, fragile desktop, or restricted desk edge may rule out a particular arm.
Keep the factory stand when the display lacks a safe compatible mount, when the desk instructions exclude clamping, or when the arm’s position and load limits do not meet your needs. A monitor riser or a different desk layout can provide height and space adjustments without attaching a moving load to the desk. Before buying, save the exact monitor and arm model numbers and compare their manuals; that makes mismatches in hole pattern, screw length, load range, and desk fit easier to catch.