Defining a clear base size

A clear base size is the anchor of every typography system. It sets the reading comfort level and determines how easily other styles can scale. Many interfaces start with a body size around 14 to 16 pixels because these values remain readable across dense layouts and support long-form content without visual strain.

Once the base size is stable, designers can build predictable relationships between styles. Using consistent units like rem helps the system scale with user settings, and sp units do the same in native environments . This improves accessibility because users can enlarge text without breaking layouts.

A reliable base size also simplifies decisions for teams. Instead of comparing arbitrary numbers, designers can generate heading and caption sizes through proportional steps, either through modular scales or grid aligned increments. This reduces decision fatigue and keeps the visual rhythm coherent across screens.

A well chosen base size also minimizes inconsistencies during handoff. Developers can rely on a single reference point instead of interpreting multiple unrelated values. It becomes easier to maintain typography tokens, test accessibility, and ensure that spacing aligns with the system’s grid.^[1]