@sequencemedia/css-purge/src/utils/get-size-in-kb.mjs

A CSS tool written in Node JS as a command line app or library for the purging, burning, reducing, shortening, compressing, cleaning, trimming and formatting of duplicate, extra, excess or bloated CSS.

export default function getSizeInKB (data) {
  const {
    byteLength
  } = Buffer.from(data)

  return (
    byteLength / 1000
  )
}