Photoshop px vs. OS px

Question

While converting a webdesign given as a photoshop file to html+css, I got confused with font sizes. As seen on the image below, 30 px in photoshop does not equal 30 px in other Windows programs (different on Mac or others?), or browsers. This seems to be unaffected by creating the photoshop image in different resolutions than 72 which is default, and unaffected by change of units between pt and px. Can anyone hint on how to set photoshop to use browser px units?

Answer 1

The font size in the paint document refers to points, not pixels. Change the font size in photoshop to 30pt and they should be the same size.

A point is 1/72 of an inch and the pixel equivalent can depend on the DPI of your monitor. At 96 DPI 30pt * 1in/72pt * 96DPI (my screen res) is 40px. To convert pixels to points work backwards so 30px * 1in/96px * 72pt/1in = 22.5pt.

So change the paint text size to 22.5 and they should match up.

Answer 2

Set it to 96 dpi.