Hit points (HP) are a numerical representation of a character or other entity's health, durability, resistance to injury, and closeness to death. Characters generally lose hit points when they take damage and gain hit points when they receive healing, and either die or fall unconscious when their hit points drop below a certain threshold.
In most RPGs with hit points, including Dungeons & Dragons and games derived from it, a player character's default and current hit points will appear as statistics on their character sheet, although some games (e.g. Unknown Armies) will make a character's current hit points a secret known only to the GM.
Hit points were introduced to role-playing in the earliest days of its development by Dave Arneson. Arneson had originally run a home game based on rules from the wargame Chainmail, but found his players weren't happy that a single hit from a monster could kill their characters. Arneson took the concept of diminishing hit points (along with armor class) on a combat system he'd used for a miniatures wargame about American Civil War Ironclads. Hit points appeared in the original set of Dungeons & Dragons and have appeared in every edition since, as well as many games inspired by Dungeons & Dragons.
Mechanics of hit points
Hit points are a representation of health or durability that are presented as numbers, specifically whole numbers (integers). (Non-numerical representations have their own type of mechanics, for which see the section on alternatives to hit points, below. There may be some overlap in the concepts.)
Hit points being a numerical representation is a simplified abstraction of health, but allows hit point values to be used and manipulated in certain ways that other representations might not, including:
- Hit points can be subject to arithmetical operations (addition, subtraction, multiplication, division, etc.).
- Hit point values (both totals and the values applied in operations) can be calculated according to the rules of the game, and may be fully or partially randomised be means of game aids such as dice.
- Hit points can have a maximum and a minimum value that cannot be crossed (barriers).
- Hit points may have any number of threshold values that have mechanical consequences or consequences in the game world of the fiction (or both) when crossed.
- Hit points can be fully or partially derived from other numerical statistics.
- Hit points can be used like other numerical statistics, e.g. used to determine a modifier for a resolution roll (although this is rare).
- Different characters (or the same character at different times) can have different default or maximum hit point values, representing different levels of durability (see the section on the meaning of hit points in the fiction, below).
Hit points generally count down rather than up (which is more common for wound systems), but the reverse is possible. There is mechanically little difference between these approaches, but there can be a psychological difference for players between having a number that dwindles to zero and a number that shows how much pain a character has endured.
Operations (damage and healing)
The most common operation that can be applied to a character's hit points is subtracting hit points equal to the damage they have sustained, and the most common source of damage in most role-playing games is as an effect of a successful attack. Games like Dungeons & Dragons and its imitators calculate damage by means of a dice pool roll only after success has been determined by a separate resolution for the attack, but there are other methods as well. Some games will calculate the effect/damage as part of a single resolution roll (although this is more common in systems without HP), others may have no random element for the attack (e.g. having fixed damage values for each type of weapon) but may allow the defender to mitigate some of the damage (e.g. if they are wearing damage-reducing armor).
Damage can be sustained from sources other than attacks, and hit points can also be lost for reasons other than damage. These alternatives (e.g. as a result of conditions, spells, or falling damage) may be calculated in different ways than as described above. In particular, some types of damage may reduce hit points by a fraction of the total hit points (either maximum total or current total) rather than an absolute value being subtracted. The simplest and most common would be to halve the hit points total (usually rounding up or down do that the hit point value is still an integer).
As well as losing hit points, hit points can also be recovered. This is usually done either by healing (by applying first aid, medicine, healing potions, or healing spells, for instance) or by resting. Healing often works as negative damage, i.e. adding to the current total of hit points, and is often calculated in similar ways (e.g. through a dice pool roll in Dungeons & Dragons). However, healing is usually either rarer or of a lower value than damage, requiring the party to leave a dungeon (or relevant dangerous area) in order to rest. Resting has different effects in different games (and may have different effects depending on the length and quality of the rest), but a typical effect of a safe and long rest is to let characters fully recover all hit points.
Calculating maximum and default HP
Characters will have both a maximum hit point value and a default or initial hit point value at which they start and to which they return when all statuses are reset (e.g. as part of a long rest). The default hit point value is almost always, but doesn't need to be, the same as the maximum hit point value.
Because hit point totals can differ between characters to indicate different levels of durability, they are often derived from other traits and choices at character creation that tie into the character's concept. In games like Dungeons & Dragons, for example, hit points are calculated by rolling hit dice, which are based on the character's class (characters from tougher classes like the fighter will have larger hit dice, perhaps d10, whereas less tough classes like the wizard will have smaller hit dice, perhaps d6). Hit points may also be derived from (or modified by) a character's other stats or attributes, e.g. increasing in line with Constitution (as in D&D) or being set initially equal to a Body score (as in Unknown Armies).
Barriers and thresholds
A barrier is a value that can't be passed when the current value of hit points increases or decreases; and a threshold is a value that the current hit points value can pass. For example, the maximum hit point total is a barrier, because any increase that might take the total above maximum instead sets the current hit points to the maximum value. (A maximum hit point value is not strictly necessarily, but is practically useful.)
For a hit point threshold to be meaningful, there must be some change in the game state (either in the game mechanics or the story) as a result of crossing the threshold. For hit points, the most common threshold is 0 HP, which may (depending on the game) kill a character outright or put them at Death's door (often unconscious). (If 0 HP does not kill them outright, there may be a lower threshold or barrier that will.)
Other thresholds may apply conditions, may change a character's capability (as in 7th Sea's Dramatic Wounds), or lead to a death spiral in which recovery becomes harder or further hit points will be lost over time (as in Apocalypse World's alternative to hit points, clocks). Changing a character's capability may be positive (giving them extra strength when they have low HP) or negative (perhaps making them unable to perform certain actions). This is not inherently ableist, but loss-of-ability thresholds are an area in which ableist design is relatively common, so designers should be careful when using them.
What thresholds exist, and what they cause or lead to, is an important decision in game design. If there is a threshold or barrier that causes unavoidable death (or other forms of finality that prevent a character from being played again) when reached, then that means that death is sometimes unavoidable in the game and that the ways death might be caused are inherent and important in the game. Designers can consider what sort of endings are important enough to encode in the game and what sort of agency the player has to affect their character's end when it happens (e.g. death saving throws or other Death's door mechanics).
Thresholds can be bi-directional (the new condition is undone when crossing the threshold in the opposite direction) or uni-directional (the new condition becomes permanent, and the threshold may become a new barrier that can't be crossed in the opposite direction). Unless 0 HP kills a character outright, it is a bi-directional threshold because healing a character will prevent them from dying and may also often restore them to consciousness.
An example of a hit point threshold in use is the bloodied condition from Dungeons & Dragons fourth edition, for which the threshold is always set at half of a character's maximum hit points. The condition has no mechanical effect on its own, but is an indication to the players (including the GM) that the character or creature has been significantly wounded, and gives an idea of pacing in combat. It may also interact with other rules (abilities, spells, etc.) that only take effect when a character is bloodied. The bloodied condition is a common house rule in Dungeons & Dragons fifth edition, even though it has no official game mechanics that interact with the condition.
Temporary hit points
Some games, including some editions of Dungeons & Dragons, allow characters to get temporary hit points separate from their usual total, and which may mean a character can have more than their maximum number of hit points. Temporary hit points usually expire after a certain amount of time (or rest) and are the first hit points lost when damage is taken.
Hit points as a pacing mechanism
As well as tracking how close individuals are to death, hit points are a key pacing mechanism. They are used to determine the lengths of combat, but they are also a key player resource that players need to manage. When a party is getting low on hit points, that can be a signal to leave an area and return to safety to rest.
Hit points may represent something other than physical durability when other sorts of situation needs to be paced. For example, in an argument, hit points might represent a character's willingness to continue and they might be forced to withdraw when they are reduced to 0 HP.
Meaning of hit points in the fiction
Hit points are an abstraction of a character's health, and there has been a lot of discussion in role-playing game circles about what they are supposed to represent in the fiction. In part, this is because hit points are used in different ways in different games, but disagreements exist even in communities that play a single game, such as Dungeons & Dragons. In particular, views differ on whether a loss of hit points on a successful attack represents a tangible, physical injury every time, some of the time, or never; and whether a certain value of hit point loss should represent a similar level of injury in any circumstance or not.
- "Hit points represent a combination of physical and mental durability, the will to live, and luck."
While the reference to "physical [...] durability" acknowledges that some attacks that cause a character to lose hit points may be physical injuries that the character can withstand or ignore, the reference to "will to live, and luck" imply that this is not always the case. However, the existence of typed damage as well as resistances and vulnerabilities mean that this doesn't always make sense in the fiction. If an attack deals a certain type of damage (say, acid damage), then the only reason a person vulnerable to acid damage would take additional damage from the attack is if they are actually struck by it. Since every attack in D&D fifth edition has a damage type, it suggests that every attack must hit. When taken to its logical conclusion, this may lead to ludonarrative dissonance.
Tim Kask (the first Publications Editor of TSR, Inc.) has said (since March 1979's The Dragon #23 at the latest) that, in old school role-playing games, hit points strictly represented the character's ability to evade a fatal blow, an ability which could be degraded over time as the character was pressed by their enemies. When hit points run out, the character can no longer avoid a fatal blow and is killed. Kask says that it would make no sense for every successful attack to be a physical injury, even a small one, because this would lead to an accumulation of scar tissue over time that would make it hard for a character to even move. Instead, the ability to evade the fatal blow covers things like fatigue, armor durability, fighting technique, fighting tricks learned, as well as simple luck. However, he also acknowledges that some attacks can land without being a fatal blow, and that attacks that bypass armor can sometimes be a reasonable way to narrate a loss of hit points from a successful attack. While this was the intention in original Dungeons & Dragons, this interpretation may not hold in other game systems.
Justin Alexander of The Alexandrian has argued that each loss of hit points from an attack in D&D is a separate hit, but that the severity of the wound represented varies depending on how many hit points the victim has. An attack that deals 1 HP can be fatal to a character with 1 HP, significant to a character with 10 HP, and largely inconsequential to a character with 100 HP. This is more in line with recent approaches in game design, e.g. from the fourth and fifth editions of D&D. As part of his argument, he presents two alternative positions (that a certain value of HP lost has a universal meaning, and that loss of HP never reflects an attack but only increasingly desperate attempts to dodge) as logical fallacies. While praising hit points as a "beautiful abstraction" that lets games like D&D work, he criticises some aspects and suggests that they could be amended to better fit his model. In particular, effects that do a largely flat adjustment to HP and do not relate to a character's competence could be made to scale with the level of the person affected. This could include healing spells and falling damage.
Other theorists have considered HP to be a measure of a character's willingness to persevere in the face of damage taken.
Alternatives to hit points
Game systems have developed many alternatives to hit points.
One of the most common alternatives is to explicitly separate the two functions of hit points that relate to ability to avoid damage (called vitality, luck, or breath) and the ability to withstand damage (called wounds). How these two stats interact varies based on game, but vitality usually varies more than wounds and is easier to recover. Vitality and wound systems have been used in the Star Wars Roleplaying Game, Fantasy Craft, as well as the computer role-playing game Pillars of Eternity.
Wounds that accumulate may also be used without a separate vitality stat. These are used in 7th Sea, Apocalypse World and others. In some cases, each additional wound level may require a more significant order of injury to be inflicted, in order to prevent the possibility of death by 1000 cuts, as in James Bond 007 (in which each wound level has its own name that starts with a different letter) and Chuubo's Marvelous Wish-Granting Engine (in which wounds can be used to give mechanical bonuses as long as the negative impacts are brought out in fiction). A similar, non-physical alternative to wounds are the marks from Night Witches, which represent accumulating trauma.
Another alternative is to give players a limited resource, stress, which they can spend to soak damage or else suffer consequences (which may be sticky like conditions or more rooted in the fiction). This approach has been used in Fate Core, Smallville, and Blades in the Dark.
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