Proficiency in a saving throw lets a character add his or her proficiency bonus to saving throws made using a particular ability score.
A successful saving throw typically either negates or reduces the effectiveness of what is being saved against.
Formula to calculate proficient saving throw.
For all saving throws that your character is proficient, we calculate it using the formula below;
Dexterity measures hand-eye coordination, agility, reflexes, and balance.
The Proficiency Bonus represents your experience from a role playing viewpoint, and your power curve from a game design viewpoint.
Calculate your proficient saving throw if you have a dexterity modifier of +3, and a proficiency modifier of +3.
Therefore, your proficient saving throw is +6.