Roblox UDim2 scale and offset
Every GUI position and size in Roblox is a `UDim2`: one pair of numbers for X and another for Y, and each number in that pair carries a scale (a fraction of the parent element) added to an offset (fixed pixels). It's that combination, not either value alone, that solves the problem of the same interface fitting both a phone screen and a 4K monitor.
Scale 0.5 moves the frame's corner to the middle of the parent (960, 540); the -100/-50 offset pulls it back by half the frame's own width and height so its CENTER, not its corner, lands in the middle.
Changing `AnchorPoint` to the element's own center removes the need for -100/-50: the calculated position now represents the center directly, not the corner.
200 divided by 1920 is 0.104166..., rounded to 4 decimal places: this is the calculation that converts a fixed measurement into a responsive fraction.
Scale is relative: a fraction of the container's size on that axis, so 0.5 means half and follows screen resizing. Offset is absolute: a fixed number of pixels added after the scale. UDim2.new(0.5, 10, 0, 0) sits at the horizontal middle of the container, plus 10 pixels, exactly the Scale × Parent.AbsoluteSize + Offset formula Roblox uses to resolve the final position.
`UDim2.new(xScale, xOffset, yScale, yOffset)` accepts all four components. `UDim2.fromScale(x, y)` is a shortcut that zeroes both offsets, useful when the element needs no fixed pixel adjustment at all.
The size is likely set in scale alone. Since scale is a fraction of the screen, a 0.3 width takes up 30% of any screen, which is a very different pixel count between a phone and a monitor. Mixing in a fixed offset locks a size floor or ceiling.
AnchorPoint does not move the element by itself: it redefines which point of the element ITSELF (a corner, the center, the middle of an edge) gets anchored to the position `UDim2` calculates. With AnchorPoint (0.5, 0.5) the position points at the element's center; with the default (0, 0), at its top-left corner.
No, it is common and intentional: a negative offset pulls the element back from the scale position, which is exactly the mechanism used to center it or to leave a margin that "reaches into" a neighboring element.
Enter the real AbsoluteSize of the Frame/ScreenGui the element will live in; the preview above is just an illustrative scaled grid, the scale values and pixel position use this size.
If you already know the position in pixels inside the container (for example, from looking in Studio), enter it here to find the equivalent pure Scale, with offset zeroed.
UDim2.new(0.5, 0, 0.5, 0)UDim2.fromScale(0.5, 0.5)UDim2.fromOffset(0, 0)Vector2.new(0.5, 0.5)Scale is a fraction of the container (0.5 = half); offset is a fixed pixel value added on top. The anchor point sets which point of the element lands at that position.
Calculation and preview run locally in your browser; nothing is sent to any server.