UPM: 1000, 2000 or even 2048. What's the difference?

Hello everyone,

Just an open question I had. What are the pros and cons of drawing a typeface based on a 1000 upm grid, 2000 or even 2048?

Depending on the typeface I’m working on I use 1000 upm or 2000 upm but never 2048. But I saw that some people do.

See this TypeDrawers thread for some in-depth notes on the topic: Units per em — TypeDrawers

At a high level, it really shouldn’t matter much in this day and age. Personally I only go above 1000UPM if the design calls for it. Microsoft recommends a UPM value for TTF files that is a power of 2, but I think it’s safe to ignore this guidance :man_shrugging:

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FYI, the Glyphs custom parameter description of the UPM:

…The value specified is the amount of units that will be used for the font size. A smaller value will cause the font to appear larger on screen, and vice versa. …

The ‘appear larger on screen’ seem to be wrong.

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That is not wrong. It means if you just change that value, and don’t scale the rest of the font, The apparent font size will change. That is a good way to adjust the rendering size (e.g. to match it to other fonts).

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Thanks. My testing code is wrong. You are right. :face_with_head_bandage: