How to Measure VESA Mount Size: 3 Numbers, Not 1

How to measure VESA mount size is a question with three answers, and almost every product listing prints only one of them. "VESA 400" tells a buyer nothing usable: 400 × 200 and 400 × 400 are different brackets, and a mount that fits one will hang crooked or not at all on the other. Add the thread size and you have the full spec. Leave it out and you have a return.

Below is the whole VESA family in one table, then the measuring method, then the number that causes more cracked display panels than any other — screw length.

Every VESA Pattern in One Table

VESA's mounting standard is formally the Flat Display Mounting Interface (FDMI), published by the Video Electronics Standards Association. It defines a set of four-hole square or rectangular patterns on the back of a display, each with a thread size and a maximum supported weight.

FDMI part	Hole pattern (mm)	Thread	Display from	Max weight	Typical use
MIS-B	20 × 50	M4	4"	2 kg (4.4 lb)	Tiny panels, embedded displays
MIS-C	35 × 75	M4	8"	4.5 kg (10 lb)	Small industrial and POS screens
MIS-D 75	75 × 75	M4	12"	8 kg (17.6 lb)	Compact monitors, POS terminals
MIS-D 100	100 × 100	M4	12"	14 kg (30.8 lb)	Most desktop monitors
MIS-E	200 × 100	M4	23"	22.7 kg (50 lb)	Large monitors, small TVs
MIS-F	200 × 200 and up, in 200 mm steps	M6 or M8	31"	50 kg (110 lb) and up	TVs and commercial displays

MIS-F is the family that scales: 200 × 200, 400 × 200, 400 × 400, 600 × 400, 800 × 400 as the panel grows. The pattern is always written horizontal × vertical, in millimetres, measured centre to centre. Which part you land in tracks the diagonal, so it is worth checking against standard TV sizes before ordering brackets in volume.

Two things about this table catch suppliers out.

First, the max weight is part of the standard, not a bracket marketing number. A 100 × 100 MIS-D interface is specified up to 14 kg. Bolting a 20 kg all-in-one PC to a MIS-D arm is outside the interface spec even if the four screws physically thread in.

Second, MIS-F moves in 200 mm steps. Spacings like 300 × 300 that turn up on some TVs sit outside that family. They exist, brackets accommodate them, but a buyer searching for "VESA compatible" will assume a standard step and be wrong.

What the Three Numbers Mean

A complete VESA specification is three values: horizontal hole spacing in millimetres, vertical hole spacing in millimetres, and the screw thread designation. Written out, it looks like 400 × 200, M6. Anything shorter is ambiguous.

Horizontal spacing — centre-to-centre distance between the left and right holes.
Vertical spacing — centre-to-centre distance between the top and bottom holes.
Thread — M4 through MIS-E, M6 or M8 on MIS-F. These are metric machine screws; the difference between an M6 and an M8 hole is invisible at a glance and immediate when the buyer tries to start the thread.

"VESA 400" is shorthand that only survives because most 400 mm patterns people meet are 400 × 400. In a product catalogue read by an overseas buyer through a translation layer, that shorthand is a support ticket waiting to happen.

How to Measure a Pattern That Isn't Labelled

Every panel arrives at a supplier at some point with no documentation. The measurement takes a minute.

Lay the display face down on a soft surface and locate the four threaded holes on the back.
Measure centre to centre between the two upper holes — that is the horizontal figure. Measuring edge to edge is the most common mistake and gives a number a few millimetres short.
Measure centre to centre between an upper and the lower hole directly beneath it — vertical figure.
Round to the nearest standard value. Patterns are designed on round numbers, so a reading of 98 mm is a 100 mm pattern plus measurement error, not a 98 mm pattern.
Identify the thread by trying a known M4, M6 and M8 screw by hand. Never force one — a forced M8 in an M6 hole destroys the insert and the panel goes in the scrap pile.

If the holes sit at the bottom of a recess, record the recess depth as well. That number decides whether a standard bracket sits flush or leaves the screws bridging an air gap, and it belongs on the drawing.

The Fourth Number Nobody Prints: Screw Length

This is where VESA hardware actually fails. The pattern gets you the right bracket; the screw length decides whether the display survives.

The standard is explicit for the large formats. For MIS-F, an M6 screw must engage at least 9 mm and at most 10 mm, and the mounting hole itself must not exceed 12 mm deep. For the smaller parts, the required screw length is the bracket thickness plus a specified engagement value — meaning the correct screw depends on the bracket you ship with, not on the display alone.

Get it wrong in either direction and you get a distinct failure:

Error	What happens	Who pays
Screw too short	Two or three threads engaged; holds on the bench, pulls out under vibration or a knock	Warranty claim, sometimes a broken panel
Screw too long	Bottoms out in the boss, then keeps turning — cracks the rear housing or punches the panel	Total loss, and the buyer blames the mount
Wrong thread forced	Stripped insert; hole is unusable at any length	Total loss

Hole position tolerance is tight enough that guessing does not work either: FDMI allows ±0.25 mm on hole position for MIS-B through MIS-E and ±0.5 mm for MIS-F. A drilled-by-eye bracket that is 2 mm off will bind on one screw and load the other three unevenly.

Where Listings Go Wrong

Look at how mount and display specs are usually written and the pattern of pre-sale questions explains itself:

"VESA compatible" with no numbers. This is the worst offender and it appears constantly on wholesale listings. It tells the buyer only that holes exist.
A single number — "VESA 200" — when the pattern is 200 × 100.
Thread omitted. The buyer orders M6 screws for an M8 interface and the shipment sits until replacement hardware arrives.
Weight limit quoted for the bracket only, ignoring the interface limit from the table above.
Screws "included" without length stated, so a buyer using a thicker aftermarket bracket has no way to know the included screws are now too short.

The fix is not more copy. It is a back-panel diagram with the two centre-to-centre spans dimensioned, the thread called out at the hole, the maximum screw insertion depth marked, and the recess depth shown if there is one. A buyer who can see the geometry stops asking, and a warehouse picking the wrong screw pack gets caught at the packing bench instead of at the customer's wall.

That diagram only works if the numbers on it were measured rather than approximated. Dimensions snapped to the actual hole centres and exported at the size each marketplace wants are a different artefact from a retouched product photo with arrows drawn on by hand — and very different from an image generator's output, which will render a confident-looking "400 mm" callout with no relationship to the panel it is drawn on. For interface dimensions, a plausible number is worse than no number: the buyer machines or drills to it. The same discipline applies whenever you label weight capacity on product images, and it is why installation clearance dimensions belong on the drawing rather than in the description.

Pre-listing checklist for any VESA product

Pattern written as horizontal × vertical in mm, both numbers present
Thread designation stated (M4 / M6 / M8)
Interface weight limit stated alongside the bracket's own rating
Screw length and maximum insertion depth given, not just "screws included"
Recess depth documented if the holes are sunk
Back-panel diagram shows both centre-to-centre spans
Non-standard spacings flagged explicitly rather than rounded to the nearest VESA size
Adapter plate part number listed if the panel needs one

FAQ

What does VESA 400 × 200 mean?

It means the four mounting holes on the back of the display are 400 mm apart horizontally and 200 mm apart vertically, measured centre to centre. The first number is always horizontal. A bracket built for 400 × 400 will not line up with a 400 × 200 panel, which is why both figures have to appear in the listing.

How do I measure VESA size without the manual?

Measure centre to centre between the two top holes for the horizontal figure and centre to centre between a top and bottom hole for the vertical figure, then round to the nearest standard value (75, 100, 200, 300, 400, 600, 800 mm). Test the thread by hand with M4, M6 and M8 screws. Measuring edge to edge instead of centre to centre is the usual source of an odd-looking result.

What screw size does a VESA mount use?

M4 for MIS-B, MIS-C, MIS-D and MIS-E patterns up to 200 × 100; M6 or M8 for MIS-F patterns of 200 × 200 and larger. On MIS-F an M6 screw should engage 9–10 mm, and the hole should not be deeper than 12 mm. Screw length must be sized to the bracket thickness in use, so a thicker aftermarket bracket needs longer screws than the ones supplied.

Is 300 × 300 a real VESA size?

It appears on real televisions, but the MIS-F family is defined in 200 mm steps, so 300 × 300 sits outside the standard series. Treat it as a non-standard spacing: state it explicitly in the listing rather than describing the product as "VESA 400 compatible," and specify whether an adapter plate is required.

How should a supplier show VESA dimensions on a listing image?

Put a rear-view spec diagram on the listing with both centre-to-centre spans dimensioned, the thread called out at one hole, the maximum screw insertion depth marked, and the recess depth if the holes are sunk. Because those figures determine whether third-party hardware fits, they need to come from measurements taken on the actual part — software that locks measured dimensions onto the image and exports at each platform's required size does that job; freehand arrows and generated artwork do not.