How far can i widen my mandible?

About 3 fingers: The average jaw opening is between 40 to 55 mm. The average person can open to the height of 3 fingers. Some people are hypermobil and they can open as much as 60 mm. Limited opening can be due to either muscle tightness or an internal derangemennt of the joint most frequently.

Unclear: Your question is a little confusing to me. Unless you have a special kind of mandibular distraction surgery, you really can't make the mandible wider. If you mean widening the opening of the mouth, that varies on your jaw joints and the surrounding muscles. Maybe you could try to re-word your question.

Surgery: Only way is surgically. If this interests you, see an oral & maxillofacial surgeon.