The Comms Creative blog on dashes:

  • Hyphens join words: eg. they’re word-joiners.
  • En dashes are a bit longer than hyphens. They’re the width of the letter ‘N’, and they show range: eg. 14–16 cm.
  • The em dash is the width of the letter M & used when emphasis is required — like when you’re trying to make a point.