Typography Legibility Grader
Grade font size, line height and line length against legibility best practice.
px
16px is the practical minimum for body copy.Multiplier of font size. 1.5 is a safe default.
chars
Characters per line. 50–75 reads best.Legibility score
100/100
Size + rhythm + measure
Font size
100%
vs 16–20px
Line height
100%
vs 1.4–1.7
Line length
100%
vs 50–75 chars
Comfortable to read — size, rhythm and measure all sit in the sweet spot. Long-form copy will hold attention, which is exactly what you need on pages that sell with words.
Guidance for body copy, not display headings. On mobile, favour 16px+ and shorter measures; the line-length ideal is about the reading column, not the viewport.
About this calculator
Score body-text legibility by comparing your font size, line height and line length against the ranges proven to keep long-form copy readable and converting.
Everything runs in your browser — nothing you type is sent anywhere or stored. Use it to sanity-check a plan, pressure-test a channel, or brief a team before you commit budget.