# How to calculate HP if an item increases constitution

I am sorry if this question seems obvious, I just cannot find the answer anywhere.

HP increase every level with the hit dice roll and the constitution bonus is added every level. What happens when the constitution bonus of the player increases because they found an item that increases constitution?

As an example, a character level 5 with 16 constitution finds at level 5 an item that increases cons to 18. Does the player get in total +4 hit point for each level or only from the 5th on?

• Quick way of calculating your bonus hit points from Constitution ability score: Ability score -10 and divide by 2 round down multiply by your level. Example Constitution 16 - 10 = 6. 6 / 2 =3. 3 x level = bonus hit points at level. Sep 18, 2022 at 0:42
• @MichaelDorf thank you very much for the tip! Sep 25, 2022 at 12:27

## Constitution Changes have Retroactive HP Changes

If doesn't matter why a character's CON changes (increase or decrease), the character's maximum HP is adjusted to match their new CON bonus. This is explicitly in the basic rules for Constitution.

If a character’s Constitution score changes enough to alter his or her Constitution modifier, the character’s hit points also increase or decrease accordingly.

This rule is why Rage increases a Barbarian's current and maximum hit points. It is why Damage or Drain to Constitution can reduce a character's current and maximum HP. This is why magical items that increase CON are desired by every character of every class.