Determine the base hit points from the character’s class, race, or creature type
Add the Constitution modifier to each Hit Die gained
At 1st level, use the maximum value of the class Hit Die plus the Constitution modifier
For each additional level, roll the Hit Die or use the fixed average, then add the Constitution modifier
Add any bonuses from feats, abilities, spells, items, or other effects
Subtract any penalties from effects that reduce hit points
Apply temporary hit points separately from normal hit points
Recalculate hit points when level, Constitution, or relevant effects change