Hit Points

Hit Points (HP) also known as Health are a game mechanic used to measure the health of a character. During combat, wounded characters lose HP. When a character gains a new level, additional HP is awarded. Should a character be reduced to 0 HP, the character dies. Needless to say, HP is an important character statistic to be monitored during play. HP can be restored using various medical items/food items such as stimpaks and wasteland omelets. HP can also be restored by sleeping or paying a doctor (both of these methods heal crippled limbs, except in hardcore mode in Fallout: New Vegas). HP can also be restored by waiting, at a rate of approximately 2 HP per 3 hours (Fallout: New Vegas).

The formulas given below generally apply only to the player character.

Fallout and Fallout 2

 * $$\text{Initial level}=15+\text{Strength}+(2\times\text{Endurance})$$

The Maximum HP increase per level is
 * $$\left\lfloor\frac{\text{Endurance}}{2}\right\rfloor+2$$

Notes:
 * In Fallout 2, the maximum amount of hit points is capped at 999.
 * The Lifegiver perk gives a +4 maximum HP per rank for each new level including level when it taken.
 * The Alcohol Raised Hit Points and Autodoc Raised Hit Points perks each increase maximum HP by 2.
 * The Alcohol Raised Hit Points II and Autodoc Raised Hit Points II perks each increase maximum HP by 4.
 * The Alcohol Lowered Hit Points and Autodoc Lowered Hit Points perks each decrease maximum HP by 2.
 * The Alcohol Lowered Hit Points II and Autodoc Lowered Hit Points II perks each decrease maximum HP by 4.

Fallout 3

 * $$\text{Initial level}=90+(\text{Endurance}\times20)+(\text{Level}\times10)$$

Example: A starting Endurance of 5 at Level 1
 * $$90+(5\times20)+(1\times10)=200~\text{Hit Points}$$

Fallout: New Vegas
Between Fallout 3 and New Vegas, base HPs were changed from 90 to 100. Further, fAVDHealthLevelMult was changed from 10 to 5. The result is starting characters from both games with Endurance 5 will have the same HPs (200) but New Vegas character's HPs scale slower than Fallout 3 characters.
 * $$\text{Initial level}=100+(\text{Endurance}\times20)+(\text{(Level - 1)}\times5)$$

Example: A starting Endurance of 5 at Level 1
 * $$100+(5\times20)+(0\times5)=200~\text{Hit Points}$$

Max health of a player character without any chem boosts, DLC or perks and at max Endurance is 445
 * $$100+(10\times20)+(29\times5)=445~\text{Hit Points}$$

Max health of a player character with DLC, chems and perks at max Endurance is 885
 * $$100+(10\times20)+(49\times5)+30^1+60^2+75^3+100^4+25^5+50^6=885~\text{Hit Points}$$


 * ¹ From Life Giver perk. ² From Buffout. ³ From Sierra Madre martini. 4 From Thought You Died perk (if Karma is at 1000 points). 5 From Black blood sausage. 6 From Battle Brew.

Fallout 4
Fallout 4's health scaling formula:
 * $$ 80 + (\text{Endurance} \times 5) + (\text{Level} - 1) \times \left ( \frac{\text{Endurance}}{2} + 2.5 \right )$$


 * Decimals are truncated in the Pip-Boy.
 * Temporary Endurance bonuses do not add permanent health on level up.
 * Health is retroactive on permanent Endurance increase.

This is a significant change from Fallout 3 and Fallout: New Vegas. The character starts with significantly less health and thus enemies feel much more dangerous. However, there are unlimited levels and thus an infinite amount of health a character can obtain.

Fallout 76
Fallout 76's health scaling formula:
 * $$ 250 + (\text{Endurance} \times 5)$$

This is a significant change from Fallout 4 because Endurance starts at 1 for every player character. As the maximum points that can be invested into Endurance is 15, there is a maximum of 325 hit points.

Losing all hit points does not always mean death, for occasionally, the player is put in the downed condition upon losing all hit points. For the next 30 seconds, it is possible to be revived by another player (by Mysterious Savior or Power Armor Reboot, if equipped) at the cost of a stimpak.

Fallout Tactics

 * $$\text{Initial level}=15+\text{Strength}+(2\times\text{Endurance})$$

The Maximum HP increase per level is
 * $$\left\lfloor\frac{\text{Endurance}}{2}\right\rfloor+3$$

Notes:
 * The Lifegiver perk gives +4 maximum HP per rank for each level gained.
 * The Brutish Hulk perk gives double the normal amount of maximum hit points each time a level is gained(deathclaw only).

Fallout: Brotherhood of Steel

 * The Die Hard skill gives an additional +20 maximum HP (up to a maximum +200) per rank.
 * The Rad Child skill allows Cain to regenerate health when others would receive radioactive damage.
 * The Sadist skill grants the ability to regenerate +2 HP for Cain and +5 HP for Nadia (up to regenerate a maximum +25 HP for Nadia and +10 HP for Cain) per rank whenever they kill an enemy.