By definition, it is equivalent to half of the body height of the typeface (e.g., in 16-point type it is 8 points).
In English, the en dash is commonly used for inclusive ranges (e.g., "pages 12–17" or "August 7, 1988 – November 26, 2005"), to connect prefixes to open compounds (e.g., "pre–World War II").
[4] Beginning in the late 18th century, compositors were frequently paid by the en,[1] rather than by the page.
In the United Kingdom, a commonly cited "standard" rate was 1,000 ens per hour, although actual compositors' output varied widely.
After the introduction of the Linotype typesetters frequently reached rates of at least 6,000 ens per hour.