How do i convert pt into em? As I use Photoshop to design templates. Software is having pt format for the text size.Then I have to transfer the design details to developers, and they always need all the text sizes in em format. I referred this site http://pxtoem.com/ for the conversions, but there is only conversion for px to em. Right now I am using 16 pt for the base font.
My another question is, Is there any difference between pt and px rather than its full form points per inch and pixel per inch.? Because I checked the height of 16pt size, its showing 16px in height only.
EM is a relative value. So the conversion is simple just cross multiply. If the body is 16px (1EM), than 2EM is 32pt and .5EM is 8pt. It works the same as percentages. One difference, percentage is 100 indexed and EM is 1 indexed.
Point is a absolute value like millimeter. A point is 1/72 of an inch. This is because a point is equal to 1/12 Pica, and 1 Pica = 1/6 inch. So 1 pt = 1/72 inch.
Pixel stands for pixel element. A pixel is the smallest unit of digital image data and without actual physical size. Screens have their pixel density measured in ppi (pixels per inch), whereas printed images are measured by dpi (dots per inch). The size of pixels depend on density of the output. A pixel can, but doesn't have to be square. An image of 10 x 10px on a LED-display (low density) is much larger than the same image printed on paper (high density).
Because a pixel doesn't have a physical size, converting it to any absolute value is only possible when you know the targeted output density. And even then you should keep in mind that modern devices give the user the ability to zoom.
Long story short: Pixel perfect Photoshop templates are outdated. If you design for screen, design the ratio between the elements. Not the actual size.
来源：https://stackoverflow.com/questions/19357839/how-do-i-convert-pt-into-em