A designer sets body text at 16px and wants standard leading. They set the leading to 8px, reasoning that this adds 8px of white space between lines. What error have they made?
ANo error — 8px is within the acceptable range for 16px type
BLeading is measured baseline-to-baseline, not as the gap between lines; 16px type needs leading of roughly 20–24px, not 8px
CThey should have used em units rather than pixels for leading
DLeading is not relevant for screen typography, only for print
Leading is measured from one baseline to the next, not as the space between the bottom of descenders on one line and the top of ascenders on the next. If type is 16px and leading is 8px, the text would overlap — the baselines would be only 8px apart while the type itself occupies 16px. Standard leading for 16px body text is approximately 20–24px (125–150% of type size), meaning the baseline-to-baseline distance is 20–24px, leaving actual visual clearance between lines. The exact distribution depends on the typeface's internal metrics.
Question 2 Multiple Choice
A designer increases line length from 55 characters to 90 characters per line, keeping type size and leading unchanged. What problem is likely to emerge?
AThe text will become harder to read because longer lines require more leading to help the eye find the next line
BThe text will become easier to read because more words fit per line, reducing the number of line returns
CNothing changes — line length and leading are independent variables
DThe text will appear too light and will need darker color compensation
Type size, line length, and leading form an interconnected system. When line length increases, the eye must travel farther horizontally to reach the end of a line, then return to find the start of the next. More generous leading gives the eye clearer vertical separation, making it easier to locate the correct line to return to. Without increasing the leading, long lines risk readers accidentally re-reading a line or skipping one — a subtle source of reading fatigue. The conventional guidance for very long lines is to increase both leading and often type size to compensate.
Question 3 True / False
Longer lines of text generally benefit from more generous leading because the eye must travel farther horizontally and needs clearer vertical separation to avoid losing its place on the return.
TTrue
FFalse
Answer: True
This is the core systemic relationship between line length and leading. At the end of a long line, the eye must scan back a long distance to find the start of the next line. If vertical separation between lines is tight, this return journey is more likely to land on the wrong line — re-reading the previous line or skipping to the one below. Generous leading creates a clear vertical target for each line. Narrow columns can survive tight leading precisely because the short horizontal distance makes line-tracking easy even without extra vertical space.
Question 4 True / False
A leading of 130% of the type size is equally appropriate for most body text regardless of the typeface or column width, as long as the type size stays constant.
TTrue
FFalse
Answer: False
The 120–150% guideline is a starting point, not a fixed rule. Optimal leading depends on the typeface's x-height (typefaces with tall x-heights like Verdana need more leading than typefaces with small x-heights like Garamond), the line length (longer lines need more leading), and the rendering environment (light text on dark backgrounds often needs more leading). Two typefaces at the same size and percentage leading can read very differently because their internal proportions differ. The guideline requires judgment based on the specific type-length-face combination.
Question 5 Short Answer
Why must type size, line length, and leading be adjusted together as an interconnected system rather than each being set independently?
Think about your answer, then reveal below.
Model answer: The three variables interact to produce the reader's experience of line tracking. Increasing line length without increasing leading makes it harder to find the next line on the return. Decreasing type size without increasing leading (as a percentage) leaves lines too close together relative to the smaller type. Increasing type size while keeping line length fixed may allow tighter leading because fewer characters per line makes tracking easier. Each change in one variable alters what the other variables need to do to maintain readability, so they must be calibrated as a system.
Designers who treat these as separate knobs often produce text that is technically within acceptable ranges but subtly uncomfortable to read. The reason readers sometimes feel fatigued without knowing why is precisely that one of these systemic relationships is slightly off: the lines are a bit too long for the leading, or the type is a bit too small for the leading. Understanding the system means being able to diagnose and adjust all three variables together.