How does first-level HP work in D&D 5e?

At level 1 you take the maximum of your first class's hit die plus your Constitution modifier. A level 1 Fighter (d10) with +2 CON starts with 10 + 2 = 12 HP. Every level after that follows the rolled or average rule.

What is the difference between max and average HP?

Max HP assumes you take the full hit die on every level-up, which is the absolute ceiling. Average HP uses the fixed value in the rules (half the die plus 1, such as 6 on a d10), which is what most groups use instead of rolling.

How is the average per level calculated?

For a die with X sides, the average gain per level after the first is X divided by 2, plus 1, plus your Constitution modifier. A d8 gives 5 per level, a d10 gives 6, and a d12 gives 7, before adding CON.

How does multiclassing affect HP?

Each class contributes its own hit die per level, but only your very first character level gets the maximum starting roll. Every subsequent level from any class uses the rolled or average value, and your Constitution modifier is added to each.

Does increasing my Constitution modifier raise past HP?

Yes. Constitution applies retroactively to every level. If your CON modifier goes from +2 to +3 at level 8, all eight levels gain 1 HP each, for a total of 8 extra hit points.

D&D Hit Points Calculator

This calculator gives the two hit-point totals every D&D 5e player needs: the theoretical maximum (full die every level) and the average fixed value most tables actually use. It handles multiclass builds by letting you stack several class rows, and it applies your Constitution modifier to every level.

How it works

Level 1 takes the full first hit die. Every level after that adds either the maximum die (for max HP) or the fixed average. Constitution is added once per character level:

firstLevelHP   = maxDie(class1) + CON
avgPerLevel(d) = (d / 2 + 1) + CON
maxPerLevel(d) = d + CON

totalLevels    = sum of levels across all classes
averageHP      = firstLevelHP + Σ avgPerLevel over the remaining levels
maxHP          = firstLevelHP + Σ maxPerLevel over the remaining levels

The first character level always uses the maximum of its hit die — this is a fixed rule in 5e, not a choice. Multiclassing simply means later levels draw their die size from whichever class you took that level in.

Example and tips

A level 5 Fighter (d10) with +2 Constitution has 12 at level 1, then four levels of 6 + 2 = 8 each, for 12 + 32 = 44 average HP; the max would be 12 + 4 × 12 = 60. For a multiclass Fighter 3 / Wizard 2, the first level (whichever class you started in) is maxed, and the rest mix d10 and d6 averages. Remember that toughness feats and similar effects add flat HP on top of the figure shown here.