When designers talk about leading, they’re not talking about mechanical pencils. They’re referring to the spacing between lines of text measured from baseline to baseline.
The baseline of a line of text is where the center of the letters sit. The leading is the amount of vertical space from the baseline of one line of text to the baseline of the next line of text. In CSS terms, it’s called line-height.
The average leading for single spaced text is around 15 points. Unfortunately, this default leading size is not legible enough. When you use a small leading size, it makes your text more difficult to read. The user can easily get distracted by neighboring text lines and lose focus of the line they’re reading.
A good guideline to follow is to set the leading to your type size plus 6-8 points. For example, if your type size is 12 points, the ideal leading for your text would be 18-20 points. Larger leading sizes create more whitespace around each text line, giving each line of text visual clarity and less noise.
After spending all that time writing the perfect text for your website, don’t ignore how users will read it. A simple adjustment in leading will make a world of difference on the user’s reading experience.