How can the CH unit help you? It is believed from many sources that the optimal characters read per line falls under somewhere between 50 - 60. The highest approved, and still considered readable length is 75 characters per line.
With the 'ch' unit (Character), you are somewhat able to set a max width based on the number of characters available to a line of text.
"This unit (ch) represents the width, or more precisely the advance measure, of the glyph '0' (zero, the Unicode character U+0030) in the element's font."
From a cross-browser viewpoint, the ch value is supported by 82.98% of web browsers according to caniuse.com.
Unfortunately, the 'CH' unit isn't very accurate, as a rule of thumb I will set my CH value to equal 10 less than a number of characters I am aiming to display.
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