Four numbers stacked, not one
The height of a screen above a desk is never adjusted directly. What gets adjusted is the stand, and the stand is the third term in a sum: floor to desk, desk to the bottom of the housing, housing chin up to the glass, then the glass itself. The top edge is wherever those four land, and the only one most people can change without buying something is the third.
Take the defaults on this page. A 29 inch desk, a stand sitting the frame 2 inches above it, a 0.8 inch chin below the glass, and a 13.3 inch panel. That puts the top of the glass at 45.1 inches off the floor with the stand at the bottom of its travel, and 48.6 at the top. If your seated eye height is 46 inches, that range brackets it and a riser is not needed; if it were 50, no setting of the stand reaches, and the difference has to come from somewhere else.
The riser only adds
This is the asymmetry that catches people. A riser, a stack of books, a laptop stand, a monitor arm at a higher clamp point — all of them raise. If the arithmetic says the panel wants to be lower than the stand can already put it, there is no product that solves it at the desk. The lever is the desk surface, the chair, or a stand with a lower minimum.
Raising the chair is the one people miss, because it feels like it should raise everything together. It does not. Raising the chair raises your eye by the same amount, so the target height goes up too, and the gap between the desk and the target closes by exactly the chair adjustment. An inch on the chair is an inch off the riser.
Where to measure from
Two measurements do most of the damage when they are estimated instead of measured. The first is seated eye height, which cannot be derived from standing height with any confidence: sitting height varies between people of the same stature by several inches, and the chair adds its own. Sit the way you actually sit and have someone hold a tape from the floor to your pupil.
The second is the chin of the bezel. Screens are quoted by their diagonal, which describes the glass and nothing else. The housing below the glass on a typical monitor is somewhere under an inch, but on a television it can be two, and on anything with a soundbar built in, more. That number goes straight into the stack, and being wrong by an inch on it is being wrong by an inch on the answer.
The tilt figure
If the centre of the panel is below your eye, the line from your eye to it slopes down, and the glass is only square to that line if it is tipped back by the same angle. At the defaults the panel centre sits 39.35 inches up against a 46 inch eye height, 6.65 inches of drop over 26 inches of distance, which is 14.35 degrees.
That is a fact about two points and a line. It is not a recommendation. Whether you want the glass square to the sight line depends on what is reflected in it, where the light in the room comes from, and what you find comfortable, and no arithmetic settles that.
What can go wrong physically
A monitor on a stack of things is a heavy object on an unstable base, and it falls onto whatever is underneath, including hands and a keyboard. A clamp-on arm concentrates a large moment into a small patch of desk edge, and a desk fastened into drywall alone has nothing to hold it. Those are hazards worth naming; how to fix them belongs to the products involved and, for anything attached to a wall or a structure, to someone who does it for a living.
Questions people ask
Why does this page not tell me the right monitor height?
Because it does not know one, and neither does any arithmetic. Published figures on screen height exist, they disagree with each other, and none of them is a fact about you. What the page does is take the target you enter — expressed as an offset from your own measured eye height, which can be zero, positive or negative — and work out what the stand, the riser and the desk have to do to hit it. If you change the target the whole answer moves, which is the honest shape of the problem. If comfort at a desk is an actual health question for you, it belongs with a doctor or a physiotherapist rather than a calculator.
The result says the stand cannot go low enough. What now?
A riser cannot help, because risers only lift. Three things move the geometry the other way. Lowering the desk surface drops the whole stack. Lowering the chair drops your eye, which drops the target, and closes the gap by the same amount as the chair moved. A different stand or an arm with a lower minimum changes the term that is actually short. Which of the three is available depends on your furniture, and the calculator will show you exactly how many inches each one has to find.
Does the frame above the glass matter?
Not for the sight-line arithmetic, which is about the glass. It matters for clearance. The top of the housing is what hits an overhead shelf, a window sill, a cabinet or a low ceiling in an attic room, and it is typically a few tenths of an inch above the glass on a modern monitor and considerably more on an older one. The page reports both so the number you check against a shelf is the right one.
My monitor is on an arm. Does any of this apply?
The stack is the same, with the arm replacing the stand: the arm has a lowest and a highest position that put the bottom of the frame some distance above the desk, and those two figures go into the stand travel fields. The difference is that an arm usually has far more range than a stand, so the answer is more often that the height is reachable and the question becomes where in the range to set it. What an arm adds is a load problem, because the weight now acts a long way from the clamp — that arithmetic is on the wall mount load calculator.
Should I use the same setup for a laptop?
The stack works identically, with two changes worth noting. The panel on a laptop is attached to the keyboard, so raising the screen raises the keys with it unless you add a separate keyboard, and the hinge limits how far the screen can be tipped. Enter the laptop screen height as the panel height and the thickness of the base as the frame below the glass, and the riser figure that comes out is the thickness of stand that puts the top edge where you asked. Whether that arrangement suits you is not something this page can answer.