Is there an optimal font size?
For most website projects I've been involved with, the font size for the bulk text is usually 12px - 13px, but I'm wondering if this is a good size. I remember reading an article saying that font sizes on websites should be much bigger, around 17px for bulk text to match printed font sizes.
Is there an optimal font size. When is something too big/small for the average user?
Is there any pro/cons for small/medium/large font sizes?
I would like to get your experience with actual tests user reactions etc. It's easy to this, this and that is too big or small, but I've learned that users sometime surprise and react differently from expert opinions.
Also the ability to change font sizes is a good discussion, but it's not what's asked for here. What I'm interested in knowing more about, is how users react to different font sizes, not how they should be able to change it.
This is a widely debated subject. One of the best ways I've seen this explained is from the presentation Design for developers: making your frontends suck less by Idan Gazit.
This had the following slide: This is 16px text on a normal screen and 12pt text in a book. The message is that 12pt is excellent for a book, but is also usually held much closer to the reader than a screen. Taking distance into account, the 16px on the screen and 12pt in the book seem about the same size. 12pt on paper = 16px on screen
There are all sorts of exceptions, where the smaller text is preferred. But for optimal readability of longer text, I agree with 16px.
It is advised to change the scalable units like em or % than the fixed-size units like pt or px. Read more: CSS Font-Size: em vs. px vs. pt vs. percent
Hmm. It seems I understand and agree with idea, but according to online calculator, 16px ***is*** 12pt. So, the answer should be a bit edited, something like this: "**Taking distance into account**, the **18px** on the screen and 12pt in the book seem about the same size. 12pt on paper = **18px** on screen".
It might be "widely debated" but only by those that don't know the STANDARDS nor the SCIENCE. For body text, best reading speed is an e-height of visual angle of 0.2 to 2 degrees, so x-height of 9.4px which is a font size of 18px or more. 18px is the suggested standard per W3C/WAI, by the way.