#layout-drift

A text element's line box measures roughly 1.5× the line-height you declare, so a column of rows built to a browser mockup's arithmetic runs long and overflows its fixed parent. Padding, borders, margins and gaps all measure exactly as declared — only the line box inflates, which is why it hides until you total a tall stack. Size fixed sub-heights from the tightest column and verify on a scale-1 capture.