5e Temporary HP & Effective HP Calculator

Resolve Temp HP stacking, Aid max-HP buffs, Damage Resistance, and incoming hit math.

Base Max HP (From HP Calc)

Current Real HP (Before Buffs)

Aid Spell Buff (Stacks w/ Temp HP)

Heroes' Feast (+2d10 Max HP)

Temp HP Source #1 (e.g., Inspiring Leader)

Temp HP Source #2 (e.g., False Life)

Damage Resistance (Rage / Aura)

Simulate Incoming Hit Damage

Temporary HP vs. Aid & Max-HP Buffs: The Exact Stacking Rules

Nothing causes more healing confusion at 5e tables than mixing Temporary Hit Points with Maximum Hit Point buffs. Because the distinction determines both your total HP buffer and whether you can be healed back up after taking a hit, memorize this single two-part rule:

Temporary HP Never Stacks: Temp HP is a separate disposable cushion sitting outside your real HP pool. You cannot add Temp HP from False Life onto Temp HP from Armor of Agathys or Inspiring Leader. When two effects award Temporary HP, you keep whichever pool you choose (nearly always the higher value). Furthermore, healing spells like Cure Wounds or Short Rest Hit Dice cannot restore lost Temporary HP.
Max-HP Increases Stack With Everything: Spells like Aid (+5 per slot level above 1st, lasting 8 hours with no Concentration) and Heroes' Feast (+2d10 for 24 hours) raise your actual Current and Maximum Hit Points. Because they are real HP rather than Temp HP, you can freely combine Aid + Heroes' Feast + one strong source of Temporary HP!

Common 5e Temporary HP & Max-HP Sources

Feature / Spell	Pool Type	Stacks w/ Temp HP?	Amount Granted	Duration & Key Note
Aid (2nd-level+ spell)	Real Max HP	Yes (Stacks)	5 HP per slot level (Lv2+)	8 hours; heals downed allies up to +5/+10/+15!
Heroes' Feast (6th-level)	Real Max HP	Yes (Stacks)	+2d10 HP (Avg +11)	24 hours; works cleanly alongside Aid + Temp HP.
Inspiring Leader Feat	Temporary HP	No (Takes highest)	Character Lvl + Cha/Wis	Free party-wide buffer on every Short or Long Rest.
Armor of Agathys	Temporary HP	No (Takes highest)	5 HP per spell slot level	Deals cold damage back while these Temp HP remain.
False Life / Fiendish Vigor	Temporary HP	No (Takes highest)	1d4+4 (2024: 2d4+4 = 9 avg)	Warlocks with Fiendish Vigor always start combat with max roll (12 in 2024).
2024 Wild Shape / Polymorph	Temporary HP	No (Takes highest)	Druid Lvl (or 3x Moon Druid)	Massive 2024 rule update keeping real HP safe underneath.

Combat Order of Operations: Resistance, Temp HP & Massive Damage

When a monster strikes your character for 40 fire or slashing damage, the order you apply math dramatically changes how long your character stays standing:

1. Apply Resistance or Vulnerability FIRST (round down after halving)
2. Subtract remaining damage from Temporary Hit Points
3. Subtract any leftover damage from Real Hit Points
4. Check Massive Damage Instant Death (if Real HP hits 0 and excess ≥ Max HP)
5. Roll Concentration Save (DC = max(10, floor(post-resistance damage / 2)))

Because step 1 happens before step 2, Damage Resistance makes every single point of Temporary HP worth twice as much Effective HP (EHP). On a Raging Barbarian with 50 real HP and 12 Temporary HP from an ally's Inspiring Leader feat, enemies must deal 124 raw physical damage to knock that Barbarian to 0 HP—not 62! Use our Resistance dropdown above to see how fast Effective HP scales when pairing high Armor Class with Rage or elemental Resistance.

Finally, watch out for Step 5 if you are concentrating on a spell like Bless or Spirit Guardians: even if Temporary Hit Points absorb every single point of an incoming attack, official rules treat any reduction to your Temp HP as taking damage, so you must still succeed on a Constitution saving throw to maintain Concentration.

Frequently Asked Questions

Do Temporary Hit Points stack in 5e?

No. Temporary Hit Points never stack. If you already have 8 Temporary HP from Armor of Agathys and gain 12 Temporary HP from Inspiring Leader, you choose which source to keep (usually the higher 12)—not 20.

Does the Aid spell stack with Temporary Hit Points?

Yes! Unlike False Life or Heroism, Aid increases both your actual Current HP and your Maximum HP for 8 hours. Because it modifies your real Hit Points rather than granting Temporary HP, Aid stacks completely with any Temporary HP source.

Does Damage Resistance reduce damage before Temporary HP absorbs it?

Yes. In 5e combat resolution, Resistance and Vulnerability are applied to incoming damage first before subtracting from Temporary HP or regular Hit Points. A Raging Barbarian hit for 20 slashing damage takes 10 damage total, losing only 10 Temporary HP.

Does losing Temporary HP still trigger a Concentration saving throw?

Yes. Even if your Temporary Hit Points absorb 100% of an attack without touching your real HP, you still took damage and must make a Constitution Concentration saving throw (DC = 10 or half the post-resistance damage taken, whichever is higher).

How do 2024 Wild Shape and Polymorph work with Temporary HP?

Under the 2024 revised rules, Druid Wild Shape and the Polymorph spell no longer replace your HP bar with a separate monster HP pool. Instead, they grant you a pool of Temporary Hit Points while using your regular Hit Points underneath.