PostCSS Ms Unit PostCSS plugin to add modular scale unit. .foo { font-size: 1ms; } .foo { font-size: 19.2px; } Usage postcss([ require('postcss-ms-unit') ]) You can also declare the ratios in root like so :root { --ms-base: 16; --ms-base: 1.2; } See PostCSS docs for examples for your environment.