Center a triangle mathematically inside a square and it will look like it is sliding toward the bottom. Center a circle the same way and it can look like it is drifting up and to one side. Software will confirm the coordinates are correct. Your eyes will keep insisting something is off, and your eyes are the ones actually being trusted here, not the ruler.
Why math and perception disagree
Mathematical centering treats every shape as a bounding box with equal weight distributed evenly inside it. Human perception does not work that way. A shape with more visual mass at the bottom, a triangle, a pyramid, a downward pointing arrow, needs to sit slightly higher than dead center to read as balanced, because the eye expects heavier forms to settle lower and compensates when they do not. A circle needs to sit marginally higher than a square of the same bounding size, because a circle's curved edges make it read as smaller than a square occupying identical dimensions. None of this is subjective taste. It is a well documented feature of how human vision processes shape and weight, and it applies whether or not a designer knows the term for it.
Where this actually shows up
- An icon nudged a pixel or two off mathematical center inside its bounding box, on purpose, so it reads as centered
- Letterforms in a wordmark spaced by eye rather than by identical numeric gaps, since some letter shapes read as tighter or looser at the same measured distance
- A logo lockup where the icon and the wordmark are aligned to their visual centers, not their geometric ones, so the whole thing reads as one balanced unit instead of two separately centered pieces
This is exactly the kind of adjustment that looks like nothing changed and feels like everything did. Compare a mathematically centered version against an optically corrected one side by side and most people cannot articulate what shifted. They can absolutely tell you the second one looks more settled, more intentional, more finished, without knowing why.
A ruler tells you where the center of a box is. It has no opinion about where a shape needs to sit to look balanced, and only one of those things matters to a human looking at your logo.