dungeons and dragons character sheet and dice 5e

You calculate hit points in 5e based on your level, your class’s hit die, and your Constitution modifier. At 1st-level, a character’s hit points equal the maximum value of their hit die plus their Constitution modifier. For example, a Wizard (d6 hit die) with a +2 Constitution modifier would start at 1st-level with 8 hit points.

Every time you level up, you can either roll your class hit die or take the average value (rounded up) and add your Constitution modifier to determine how many hit points you gain. For example, a Wizard with a +2 Constitution modifier can either gain 1d6 + 2 hit points when they level up, or they can automatically take 6 hit points (1d6 average = 3.5, rounded up to 4, +2).

Starting Hit Points by Class in 5e

Class Starting Hit Points
Artificer 8 + Con Mod
Barbarian 12 + Con Mod
Bard 8 + Con Mod
Cleric 8 + Con Mod
Druid 8 + Con Mod
Fighter 10 + Con Mod
Monk 8 + Con Mod
Paladin 10 + Con Mod
Ranger 10 + Con Mod
Rogue 8 + Con Mod
Sorcerer 6 + Con Mod
Warlock 8 + Con Mod
Wizard 6 + Con Mod

Average Roll Results by Hit Die in 5e

Hit Die Average Result
d6 4
d8 5
d10 6
d12 7

Player’s Handbook, page 12

Retroactive Hit Point Gains

If your character’s Constitution modifier increases, you retroactively gain +1 hit point for every character level you have, minus 1. For example, if you increase your Constitution modifier from +2 to +3 upon becoming 8th level, your character would gain 7 hit points from this (as well as use the new +3 Constitution modifier for determining hit points gained from this new level up).

This applies to all Constitution modifier changes, both positive and negative, permanent and temporary. For example, if a magic item increases a 10th-level player’s Constitution modifier by +2, that player gains 20 maximum hit points.

Alternatively, if a player’s Constitution modifier is reduced by an effect, their hit points are also reduced. For example, if a monster’s curse reduces a 5th-level player’s Constitution modifier by -1, that player loses 5 maximum hit points.

Player’s Handbook, page 177

Note that this also applies to the Tough feat, which grants +2 hit points per level, both after taking it and retroactively. For example, if an 8th-level player gains the Tough feat, they instantly gain 16 hit points (PHB 170).