Resize Letter

This tool computes precise changes to letter sizes and related line-height metrics when moving from a current font size to a target size. It supports multiple units (pt, px, em, rem) and can batch process several blocks. Conceptually, it converts both sizes to a common basis, computes a scale factor, and applies that factor to the line-height when provided. The result includes a new font size in the chosen unit, a unitless scale factor, and an updated line-height value. It outputs a CSS-ready snippet or a JSON config for downstream pipelines. Users include designers preparing style guides, editors aligning typography across languages, and developers implementing responsive typography rules. Unique value comes from explicit unit handling, safe fallbacks for em/rem with a base font, and ready-to-export metric data that avoids manual recalculation across blocks. Core features include unit conversion, batch support, and export formats; core logic enforces linear scaling only and does not adjust kerning or glyph metrics. Use cases include converting font sizes between print (pt) and web (px), scaling headings consistently, and generating reusable typography configurations for design systems.