A useful starting point
A modular scale multiplies a base size by the same ratio at each step. It creates a consistent set of sizes to try, not a rule for how every language or design should look. Test long headings, real paragraphs and narrow screens before choosing.
Formula and worked example
At step n, size in CSS pixels = base × ration. Divide by the configured root size for rem. With a 16px base, a 1.25 ratio and a 16px root, step 2 is 25px or 1.5625rem. Negative steps divide by the ratio. The calculator shows steps −2 through 6.
CSS export rounds rem to four decimal places and includes pixel comments. It intentionally does not set the document’s root font size. Specimens larger than 96px are capped visually and labeled; the calculated values remain unchanged. Small sizes are included for comparison and may be unsuitable for readable body text.
Units follow W3C CSS font-relative length definitions. Compare chosen fonts in the font workspace and check color contrast.