How does zoom scaling correspond to pixel height?

This is related to a previous post asking about a grid overlay, but it’s a different question. For this hymnal project, I have been asked to align the layout as closely as possible to a 12-pt vertical grid (I know this is not practical for music, but that’s just what I need to shoot for as much as possible, so I’d rather not discuss the merits of their request here).

My question is how zoom scaling corresponds to points and pixels. In the screenshot below, I’m on a monitor with a vertical resolution of 2160px, scaled to 200% (I have no idea if that is pertinent). Dorico is viewing at 150%. The selected text frame has a height of 60pt, and the grid overlay has a pixel height of 60 pts. However, that would be a 15-pt grid, which is not quite what I want, and I don’t really know how to work out the math.

Can anyone help me make sense of this muddle? I need to use this screen overlay to align as many elements on the page as possible, but I want to understand better how zooming in Dorico relates to pixels and points so I can have confidence to know what kind of a grid I’m aligning to. Thanks in advance, for anyone who is still reading this…


I think I’ve worked out that a 36px screen overlay will correspond to 12 pts on the page at 150%. Does that sound right? That would mean I need to work at 150% or 300% only?

At what zoom size is the page at “Actual size”, e.g. holding up a sheet of paper over the screen fits the on-screen page?

That info, and the ‘pixel density’ of your display, may be relevant info.

I’m aware that Windows and Mac do scaling in different ways, so I can only speak for how Macs work. But maths is maths.

Assuming you’ve got a 27 inch 4K display, your pixel density is 163ppi.
If it’s a smaller or larger size display, you’ll need to work it out.

At Actual Size, then a 163ppi display has 2.27 pixels per point.

The 200% scaling is very relevant, as it effectively means that everything is twice as large as it should be! You’re now working to 81.5 pixels to the inch, just with twice the detail/smoothness.

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