AC vs. HP Tradeoffs in D&D 5e Character Building

Armor Class and Hit Points both keep you alive. AC prevents hits. HP absorbs them. Which matters more?

The Math

Higher AC = fewer attacks land = less damage.

Higher HP = attacks that do land deal proportionally less of your total HP pool.

Both reduce incoming damage over time.

Quick Math

Imagine a character with AC 15, 30 HP, facing an enemy that hits on 10+ and does 10 damage per hit.

• Per round: 55% chance to hit x 10 damage = 5.5 damage.
• HP lasts: 30 / 5.5 = ~5.5 rounds.

Same character with AC 20, 30 HP:

• 30% chance to hit x 10 = 3 damage.
• HP lasts: 10 rounds. Nearly double.

Same character with AC 15, 60 HP:

• 5.5 damage/round for 10.9 rounds.

AC and HP both double survivability equivalently.

Situation Matters

AC Is Better When

• Attackers have moderate hit bonuses. +5 to hit means raising AC from 15 to 17 = 10% fewer hits.
• Many small attacks. AC stops each one from landing.
• Attacks can't reroll. Advantage or high hit bonuses diminish AC's value.

HP Is Better When

• Attackers have high hit bonuses. Against +12 to hit, AC 22 vs. AC 18 is only 20% fewer hits. HP's effect is linear.
• AOE damage. AC doesn't help against most AOE (Dex save replaces AC).
• Big single hits. Adding 20 HP lets you take one extra big hit.

Best Practice

Both matter. Don't sacrifice one entirely for the other.

Target:

• Level 5: AC 18, 50+ HP.
• Level 10: AC 20, 90+ HP.
• Level 20: AC 22+, 180+ HP.

AC Sources

• Heavy armor. +max at 18-19 base.
• Shield. +2.
• Dex mod (light/medium armor).
• Spells: Shield (+5 reaction), Shield of Faith (+2 concentration).
• Magic items: Ring of Protection +1, magical armor.
• Class features: Defense fighting style (+1), Barbarian Unarmored Defense.

HP Sources

• Hit die. d6 to d12 per level.
• Con mod. +per level.
• Feat: Tough. +2 HP per level.
• Species: Hill Dwarf. +1 HP per level.
• Aid spell. +5 max HP for 8 hours.

Solo Play Considerations

Solo characters need both:

• AC to reduce hits in long encounters.
• HP to survive boss crits.

Best Solo Durability

• Mountain Dwarf Paladin (Plate + Shield + Aura + d10 HP + Con proficiency).
• Hill Dwarf Cleric (heavy armor + extra HP + healing).
• Half-Orc Barbarian (Rage resistance + d12 HP + Relentless Endurance).

Shield Spell Is a Special Case

Shield (+5 AC reaction) is situational AC. Use when a hit will land. Effectively costs a 1st-level slot for "the most dangerous hit this round doesn't land."

In The Endlessness

Our AI Dungeon Master tracks AC and HP continuously. When attacks happen, AC is checked first, then damage applied.

For related reads, our armor class guide, hit points guide, and building a tank cover more.

Final Takeaway

Balance both AC and HP. Don't neglect one. Target AC 18+ and HP appropriate to your level.

Start a character at The Endlessness and feel the difference high AC and HP make.