Font size, line height and line width the golden ratio way

Kareem Elansary
Jun 7, 2015 · 3 min read

For the past few days I had this question in my mid
what is the best line height value for 14px font size on my screen?”,
I start digging everywhere on the web to know how people calculate it, and I got some interesting numbers:

Line Height

Twitter bootstrap is using a (1.42857) as a ratio between the font size and the line height ( line-height = font-size * 1.42857).
HTML5 boilerplate using almost the same value which is (1.4).

Medium and zurb foundation framework they are using the same ratio for the line height and it is (1.5).

And just for your information adobe topcoat is using (1.313) and yahoo purecss is using (1.58), so which one should I use?

Note that 1.5 is a value that is commonly recommended in classic typographic books, so our study backs up this rule of thumb. :smashing magazine

Personally I don't know which one to use, is it old industry numbers or unknown magical numbers? can I create my own number?

The nature gave us an incredible proportion and it is around us everywhere known as the golden ratio (1.618). So I will use ( 14px * 1.618 ) as my line height, ok I know the answer to my first question but another question just jumped to my head
“what is the best line width for 14px font size and 23px line height?

Line Width

So how I can figure out the a relation between the font size and the line width? all what I know here is the line width is significantly greater than the line height, and thats a good start for me.

After reading some researches about the best CPL (character per line) I found that 60%+ of people reading faster with 70 CPL and here you are the summery:

Medium line length of 55 cpl for ease of reading, better comprehension and better reading rates for on-screen text compared to lines of 25 cpl or lOO cpl.

Optimal line width for a single column of text ranges from 45 to 75 cpl. For multiple columns, the line length should be 30 to 50 cpl.

Line length should be around 30 times (between 20 to 40) the size of the font type

Readers prefer short lines of about 8 to 10 words or 45 to 60 characters long

There is no fixed value here for the line width, its something between
(30 cpl — 90 cpl) or (8 words— 12 words).

lets do the final step by calculating the line width:
line width = average character width * cpl
average character width = font size / character constant (**)

So finally:
font size = 14px
line height = (14*1.618) = 23px
width @ 50cpl = 50*(14/1.618) = 433px

Live demo

I created [ this ] demo so you can try different line-height and line-width combinations.

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