The reading problem
Inspect line length while remembering that character counts are only clues.
A concrete example
A paragraph at 16 px in a wide email window will wrap differently from the same words on a phone or in a different font. A “65 characters” target is not a physical width and cannot certify a page.
Try this edit
Paste a short paragraph into Paragraph Measure, choose a character cap or a pixel preview, and compare the displayed lines. Read the paragraph at your normal size and again enlarged; revise the container, not just the number.
Proof on the page
Use the same paragraph twice: first at 18 px and 560 px width, then at 22 px and 420 px. Record the average and longest displayed line in each preview. The words have not changed, but the line breaks should. If a longer word extends beyond a character cap, the tool states that exception. This experiment shows why a single character figure cannot describe every presentation.
Where the method stops
The W3C visual-presentation criterion includes more than line width and sits at Level AAA; this worksheet is not a test of that criterion. It does not inspect colour selection, justification, spacing overrides, zoom, surrounding controls, or a real document’s font. Keep a human checklist and test the actual page before making any accessibility claim.