If the distance between the tip of tongue and insertion of lingual frenum is 6 mm, then it will be:
Class 1 - Mild ankyloglossia - 12-15 mm
Class 2 - Moderate ankyloglossia - 8-11 mm
Class 3 - Severe ankyloglossia - 4-7 mm
Class 4 - Complete ankyloglossia - 0-3 mm.
Mild ankyloglossia
Moderate ankyloglossia
Severe ankyloglossia
Complete ankyloglossia