Proportio is an open-source web app for building proportional scales - ratios you can apply consistently to type sizes, spacing, icons, and component dimensions in a design system.
Instead of picking sizes by eye, it lets you set a ratio and base value and generates a consistent scale you can export as W3C design tokens or CSS variables.
Useful for design systems teams who want their typography and spacing scale to actually share the same underlying math.
Free and open source, built by Nate Baldwin with the code on GitHub; runs entirely in the browser, no account needed.
