How long does a sprained ankle heal completely?

Healing of sprain. This varies according to the severity of the sprain and the health and age of the individual. It also varies whether it is treated or not. Some sprains may heal in 3 to 4 weeks while others linger for many months. In the worst case scenario, healing remains incomplete and leads to chronic ankle instability.
Depends. Depends on how severe the sprain, what ligaments involved and how it is treated.