Digital content design system techniques are described using baseline units to control arrangement and sizing of digital content. In one example, a digital content design system receives a user input specifying a number of baselines to be included within an available display area of a page. Baselines are used to align digital content to control arrangement of the digital content within the page, e.g., text. From this, the digital content design system then calculates a baseline unit from a distance used to space adjacent baselines of the number of baselines from each other. This baseline unit is then leveraged by the system as a fundamental unit of measure to control arrangement and/or sizing of digital content in relation to each other.