cynwoody on In CSS, “px” is not an angular measurement and it is not non-linear

Comment on In CSS, “px” is not an angular measurement and it is not non-linear parent

but OS X treats it as 72dpi

I just added a 960px <hr> to this web page. On my monitor, attached to a MBP running OS 10.6, it measures about 9.5 inches (by holding up a ruler to the screen). That would indicate OS X treats my screen as about 100 dpi.

The monitor is 30" diagonal, 2560x1600. So, calculating the dpi:

    irb(main):010:0* ratio = 1600/2560.0
    => 0.625
    irb(main):011:0> width = 30.0/Math.sqrt(1 + ratio*ratio)
    => 25.4399491201526
    irb(main):012:0> dpi = 2560.0/width
    => 100.62913207527

One of these days, I'm going to get around to buying a new Retina MBP. Then, I'll try that exercise again.

jahewson 12y

Yep, that's because it's 960px in CSS pixels, which are at 96dpi. Your monitor also has it's own physical dpi so you can't just measure the length of a line on the screen to infer the OS's dpi.

Comments