Letter height, relief and legibility
Letter height is the cap height of the text, while relief is how far it rises above the face. The two are independent: you can print 20 mm letters with only 1 mm of relief. Legibility follows letter height, and how the text feels under a finger follows relief.
A door plate read from across the room wants 15 to 20 mm letters, while a key tag held in the hand works at 8 to 10 mm. For relief, 1 to 1.5 mm is right in most cases; 3 mm and up makes a two-colour print easy to execute.
- 6-8 mm text: key tags and small bin labels
- 10-14 mm text: cabinet, drawer and shelf labels
- 16-24 mm text: door plates and signage read from a distance
- 0.8-1.5 mm relief as standard, 2-4 mm for two-colour prints