The font size or text size is the overall size (generally height) of a font shown on a screen or printed on a page. A font is typically measured in a point (pt) size, which is the vertical measurement of the lettering. There are approximately 72 (72.272) points in one inch or 2.54 cm. In the picture above are examples of font sixes 6pt to 84 pt.
Although points are the traditional measurement of fonts, with computers and other screen displays font sizes are also measured as pixels (px) and in pica (pc).
The font size may also be measured in em space, which is the width of the font generally equal to the point size.
With web design and CSS, a font size can be set as pre-determined font dimensions using: xx-small, x-small, small, medium, large, x-large, xx-large, smaller or larger keywords. The font size can also be specified using the point, pica, inch, centimeter, millimeter, em and percentage.