Convert a length between the five most common CSS units: px, rem, em, pt and %. Type a value in any field and the other four update instantly. rem is computed against the root font size (the html element, 16px by default), while em and % are computed against the parent element's font size, which you can set separately for nested contexts.
The conversions use the standard web relationship 1pt = 1/72 inch and 1 inch = 96px, so 1pt ≈ 1.333px. This is handy when translating a print or design-tool measurement (points) into responsive web units. Everything is calculated locally in your browser.