The Alexandrian

Explaining Hit Points

January 28th, 2008

Hit points have been around for more than 30 years now. (Longer if you count their antecedents in wargaming.) So you might think that, by now, people would have a pretty firm grasp on how these mechanics worked, what they represented, and what it means to lose hit points.

You might think that. But you would be horribly mistaken.

Basically I’m writing this little mini-essay because I’m tired of engaging in the same painful debate every two months. I want to be able to simply point people to this essay and say, “Look, this is the way it works.” (This won’t actually have much effect with people who prefer to be mired in fallacies and foolishness, but it will at least delay the day on which I will inevitably succumb to a lethal case of carpal tunnel syndrome.)

So, first I’m going to repudiate the two primary fallacies which lead the innocent astray when it comes to understanding hit points. And then I’m going to pull my Big Reveal an explain the beautiful abstraction which lies at the heart of the hit point system.

(It should be noted that this essay specifically deals with the type of inflationary hit point system found in D&D. The term “hit points” may also be used for very different damage tracking systems, to which this essay probably won’t apply at all.)

FALLACY THE FIRST: THE AXE TO THE FACE

The first fallacy goes like this:

1. Dupre has 100 hp.

2. A goblin with an axe has hit him 10 times and done 78 points of damage.

3. Clearly, the goblin has hit Dupre in the face 10 times and Dupre is still alive! That’s ridiculous!

The fallacy lies in the illogical leap from point 2 to point 3. A moment’s consideration clearly reveals that there is absolutely no reason to assume that, every single time the goblin landed a solid blow, it meant that the goblin planted his axe straight between Dupre’s eyes.

For example, imagine that you’re talking to someone in real life and they said, “Did you know that Bill was actually shot three times during a mugging a few years back?” Given that Bill is still alive, would you immediately assume that, during the mugging, Bill was dropped to his knees, a gun held to his head execution-style, and the trigger pulled three times?

Of course not. You would assume that Bill was probably hit in the legs or the arms. If he was hit in the chest, you’d assume that he only survived because he got prompt medical attention. And if one of the bullets actually did take him in the head, you’d know that it was a medical miracle that he was still alive.

Similarly, there’s no reason to assume that Dupre was hit in the face ten times with an axe. In fact, quite the opposite is true: There is every reason to assume that he wasn’t hit in the face ten times with an axe.

FALLACY THE SECOND: DEATH BY DODGING

The second fallacy is most often committed because, after escaping the trap of the first fallacy, people go to the other extreme:

1. Dupre could not have been hit 10 times in the face with axe and survived.

2. Therefore, Dupre was never hit with the axe.

3. Dupre won’t be hit by the axe until a blow causes his hit points to drop below 0. When that happens, the goblin will have finally hit him with the axe.

The fallacy here lies in the leap from point 1 to point 2.

Let’s go back to the example of Bill’s mugging. If you friend said to you, “Did you know that Bill was actually shot three times during a mugging a few years back?” Would you assume that he meant, “The guy mugging bill shot his gun three times, but never actually hit Bill.”?

Of course not.

In terms of D&D, the nature of this fallacy is more explicitly revealed when you look at something like poison. If the orc’s axe is coated with poison and we embrace this fallacy, then Dupre has been exposed to the poison 10 times despite the fact he’s never actually been hit by the axe.

And you can reproach this fallacy from multiple directions: If the hit point loss from blows that don’t “really” hit is because Dupre is wearing himself out from dodging, why is dodging a +1 flaming sword more exhausting then dodging a +1 sword?

And, of course, you also have the oddity that, apparently, dodging a blow from a sword can be even more deadly to you than being hit by the sword.

THE BEAUTIFUL ABSTRACTION

The trick to understanding the hit point system is understand that a hit point is not equal to a hit point. In D&D, 1 hit point of damage always represents a physical wound. However, the severity of the wound represented varies depending on how many hit points the victim has.

For a character with 1 hp, that 1 hp of damage represents a serious wound — a punctured lung, a broken leg, or something of that ilk.

For a character with 10 hp, that 1 hp of damage represents a meaningful wound — a deep but or a broken rib.

For a character with 100 hp, that 1 hp of damage represents an essentially inconsequential wound — a scratch, a bruise, or the like.

The reason any particular character has fewer of more hit points (and, thus, varying the severity of any given wound they receive) is abstracted. For some characters its skill; others luck; others physical toughness; others divine grace; others magical protection; and so forth. For most PCs, it’s some combination of all these things.

This is a beautiful abstraction because it allows for quick, simple, and entertaining gameplay. One could certainly design a system with variances in skill, luck, toughness, divine favor, magical protection, and the like were all separately modeled. Many such systems exist. But none of them are as simple, easy, or fun or as hit points have proven to be.

IS IT PERFECT?

No. The system is an abstraction, and that brings with it both advantages and disadvantages. The advantages are simplicity and completeness. The disadvantage is that you can’t reliably pull concrete information back out of the abstraction — and, if you try, you’ll eventually find corner cases where seeming absurdities crop up.

For example, it’s theoretically possible for a sufficiently weak character to deal no more than 1 hp of damage per attack. Such a character could, theoretically, land 100 blows on a character with 100 hp before taking him down. Add poison to the scenario, and you’ve now locked yourself down to a scenario where the weak character is, apparently, whittling his opponent to death.

Such corner cases are statistical oddities, but they’re going to reliably crop up in any system which doesn’t require several additional orders of complexity.

Which leaves the only significant and intractable problem with the hit point abstraction: The cure spells. Despite the fact that the number of hit points required to represent a wound with a particular severity varies depending on the character’s total hit points, a cure spell heals a flat number of hit points. Thus, a cure light wounds spell used on a 1st level fighter will heal grievous wounds. When the same spell is used on a 10th level fighter, on the other hand, it can’t handle more than a scratch.

This is a legacy issue which has been retained for reasons of game balance. But if you want to fix this, simply have cure spells work more like natural healing: Multiply the number of hit points cured by the creature’s HD.

Hit points aren’t a one-size-fits-all solution to tracking wounds in roleplaying games. There are lots of reasons why you might want a more concrete representation of actual wounds or a realistic modeling of incapacitation.

But hit points are often attacked for the most erroneous of reasons. And, as I said up front, I don’t necessarily expect this little essay to make any sort of huge dent in that tidal wave of ignorance and faulty logic. But it might help me keep my blood pressure down.

6 Responses to “Explaining Hit Points”

  1. Justin Alexander says:

    ARCHIVED HALOSCAN COMMENTS

    Matt
    I’ve always considered hit points to represent a combination of physical endurance and, crucially, morale.

    For me hit points don’t just represent your physical condition – they represent a willingness to keep fighting. That’s what really seperates the truly tough from the combat averse. What makes you and I different from a Mafia soldier is not simply our relative skills with a 9mm automatic or our health – it’s the willingness to pull the trigger. And to keep aiming and pulling the trigger while someone is firing back.

    So in my games hp ‘damage’ can be psychological – a flaming sword whistling past your ear and singing your hair can do damage by being intimidating. A near miss which lets the player see the venom dripping from the blade, an axe thunking into the tree by a player’s head, bullets pinging off the wall around him… all these things can represent a loss of hit points.

    I like the narrative element and tension which that can build into a game because melee isn’t a case of describing a series of attritional blows – or in the case of 20th century stuff, constantly trying to pass off gunshot wounds as some sort of trivial graze.

    Within the D&D world it’s still a consistent rationale as each hit point loss effects a lvl 5 fighter far less than a lvl 1 fighter (as a smaller proportion of the total hp) because the lvl 5 guy is experienced rather than green, more determined, more gutsy, more heroic.

    It also makes sense when the goblin makes a break for the door on 1hp. A goblin with 6 serious sword wounds is in no condition to run anywhere – he’s in intensive care. The goblin runs because he’s bottled it, not because he’s down to his last limb.

    It also means ‘healing’ can be as much motivational as physical. A healing potion could be a glowing blue phial or a bottle of Nuka Cola or a nice flask of tea for all I care. It could be a rallying cry or the sudden arrival of reinforcements or seeing an ally down an enemy, whatever is right to reinvigorate the character for the fight ahead in a way which enhances the story.
    Thursday, November 25, 2010, 8:25:34 PM


    Andrew Chirgwin
    Justin,
    I read this after I started work on my own RPG System. After having debates about the “HP/Wound Points” system used in things like Star Wars Saga (as I understand) where you have a certain number of points to represent your physical self (and critical attacks target these special Wound Points, but normal attacks do not until you run out of HP) I sat down and looked at what HP seemed to represent.

    My conclusion was that HPs actually represented Combat Stamina. Rocky, with his significant and frequent unarmed combat training can have the almighty CRAP beaten out of him by many people and take bullet wounds and still continue. Me as an out of fitness highschool teacher with little combat training should be beaten to an unconscious pulp in moments.

    Rocky has many many stamina points, can take a significant and violent beating before becoming unconscious. Me, I might have maybe 5 stamina points… on a good day? Rocky there, the combat machine should rightfully land one decent blow on my nerdish jaw and have me on the ground cold and bleeding.

    So thanks for after-the-fact confirming my convictions about what HP are.
    Tuesday, June 22, 2010, 4:09:28 AM


    Justin Alexander
    Depends on what you’re trying to accomplish. Yes, in real life there’s no way for even the most amazing athletes to mitigate falls from great heights.

    However, in the realm of heroic pulp fiction the great heroes do have that ability. So, personally, I don’t have much of a problem with falling damage: For low level characters, falls are still plenty dangerous. For mid-to-high level characters they’re more survivable, but these are also the levels where characters begin transitioning into being the equivalent of demigods from Greek myth, so it doesn’t feel wrong to me.
    Wednesday, August 06, 2008, 1:18:36 PM


    Axcalibar
    What’re your thoughts on falling damage? Personally I think 1d6/10′ is far too low. Hitting the ground is ostensibly physical damage, and there is really no way to minimize that damage the way one would endure cuts and bruises. Though some IRL have survived significant falls, it’s not the sort of thing one can get up and walk away from. My house rule is “cocky barbarian who jumps off a 300′ cliff claiming he can take it” becomes “ground-pudding”.
    Wednesday, August 06, 2008, 12:27:44 PM


    Malimar
    Well, I think falling damage kind of goes back to Calibrating Your Expectations ( http://www.thealexandrian.net/creations/misc/d&d-calibrating.html ).

    An average human, ie a 1st or 2nd level commoner with the average ability score array, will have somewhere between 1 and 10 hit points. Such a person can easily go unconscious from as little as a 10-20ft fall (1-12 damage) , and die instantly of a 40ft fall (4-24 damage) which seems to me fairly reasonable.

    The most super-epic humans who have ever lived on Earth are about 5th level. Conan, Aragorn, and Einstein are all 5th-level characters. Rough estimates: Conan the 5th-level Barbarian probably has about 37hp, Aragorn the Rgr1/Ftr1/Pal3 has about 31, and Einstein the 5th-level Expert has about 10 (as calculated in the linked essay).

    I don’t know what sorts of falls these characters have canonically survived, but Conan could concievably die instantly in an 80′ fall or survive a fall of any height; Aragorn could die in a 70′ fall or survive a fall of any height; Einstein could die in a 40′ fall or survive up to a 180′ fall.

    (Falling damage is capped at 20d6 for terminal velocity, so if you can potentially survive a 200′ fall (ie, if you have at least 11hp), you can survive any fall just as well.)

    The longest fall ever survived without a parachute was 33,330′. But that was a perfectly average level 1 or 2 flight attendant, who should have at most 8hp and thus should be able to survive a fall no greater than 180′, which means, barring divine intervention or house rules, the falling damage rules are actually too harsh to model real-world extremes. Maybe flight attendants (and all people who have ever survived falls from a height of 200′ or greater) count as Experts instead of Commoners, in which case she could have as many as 12hp and could indeed have survived such a fall and the problem goes away.

    To have absolutely no chance of dying instantly in a 300′ fall, the cocky barbarian needs to have at least 110hp (20×6=120), in which case he’s an Elite character of at least 8th level or an Average character of at least 9th level who has rolled perfectly on almost all his hit dice, or he’s level 15 or 17 with average hit dice rolls. ie, he’s higher level than any character found in almost any fictional setting and approaching demi-god-hood and legit should be able to shrug off falling from such a height. Other classes, with smaller hit dice, need to be even higher level.

    In conclusion, like many things in 3.5e, once you’ve Calibrated Your Expectations(tm), the falling rules make a buttload more sense.
    Sunday, June 06, 2010, 12:41:39 AM


    Todd Kes
    One other stunt, if you want to go slightly away from the hit point method, is to have hit points, and then a wounds value. Hit points reflect the person’s ability to ignore minor stuff, cuts, scratches, exertion, etc. The wounds reflect actual life threatening stuff, and would be equal to the hit dice.

    This allows the 1st level goblin thief to backstab a warrior, because the backstab goes directly to the wounds. Figure any attack that surprises, or does area effect applies directly to wounds, while directed attack that beats the armor only goes to hit points.

    Also, each wound lost will cause a successive loss of hit points as well (you are badly bleeding, so it is causing steady loss of strength).

    Hit points would be healed easily, but wounds would require dedicated magic. Cure minor, light, moderate, and severe wounds would heal 1, 2, 3, or 4 wounds respectively.

    I admit this will cause perception and spot checks to become critical skills and abilities, not to mention that trap makers will be having fun.
    Sunday, February 03, 2008, 6:51:43 PM

  2. d47 says:

    Dupre is passed out drunk. Goblin sneaks into his camp, lines up his axe with Dupre’s neck, and swings. Do you ignore HP and just say, sorry Dupre, you’re now dead, or do you explain the shaving nick received from the Goblin axe as a combination of divine intervention, luck and +5 aftershave?
    Yes, I think you do (one or the other), depending on your game style.

    One problem with high HP is that they encourage violence as the first solution when PCs encounter “weak” monsters. They also turn many fights into dull grinds. I want players to always feel that there is some risk in any battle (even with mooks), both for game excitement and out of preference.

  3. MS Kati says:

    My problem with these varying interpretations is that they seem to be accounted for elsewhere. For example, the first commenter states that HP is a combination of physical health and morale. However, morale is it’s own thing; a character can be scared or demoralized without ever having been injured, and it is never going to kill them. The demoralization would be better expressed as a penalty of some sort; this person is not going to take the most effective action anymore, because they aren’t in the right frame of mind. The penalty is never going to kill them, though (it may get them killed, which is appropriate, but they won’t die from the penalty itself.) By the same token, if i’m in a fight, and someone just cut me a bit, I am still perfectly capable of effective action, perhaps even more so now that adrenaline is pumping. However, that cut may eventually kill me, so it is rightly expressed as hit point loss.

    Another example, it was stated that you could consider your magical and non-magical defenses to be part of your HP. No, those defenses are expressed as your AC, defensive spell effects, etc. Your spellcaster rolls a lower HP dice than a fighter because the spellcaster has devoted their life to the acquisition of knowledge and not, say, jogging (to paraphrase OOTS.) The spellcaster can then defend themselves with spells or other means to make up for it, but that will rely on them not taking the hit. If Rocky punches me in the jaw, i’m losing hit points. If Rocky punches me, but it stopped by a metal plate or an eldritch force before he connects with me, i’m not losing hit points.

    Therefore, I believe hit points should be thought of as the following: a representation of physical damage, with the amount of damage being represented by the percentage of hit points lost. This is essentially what the original post suggests, but the reasoning behind it doesn’t make sense to me. It isn’t that some people can take greater physical damage due to skill or magical defenses, they can take greater damage because they are tough. The tough fighter can take more hits than the dodgy rogue because the rogue expects to be dodging, they don’t want to take the hits, while the fighter will be tanking, they wants to take those hits. The rogue will have fewer HP and higher AC than the fighter to represent this. The skill, the magical defenses, the divine favor, these are all mechanics other than HP.

    Does this make sense as written, or just in my head?

  4. MS Kati says:

    Thinking about it a bit further, healing has to be a flat amount of health and not a percentage. If a 10 HP Wizard and a 30 HP Fighter take the same 4 damage axe wound, the wizard is going to be smarting, while the fighter is still more or less fine. The cleric walks over to both of them and analyzes the wounds.

    Method 1: Flat healing. The wizard has a gash six inches wide and an inch deep. The cleric determines this is a light wound, and can close it easily with Cure Light Wounds. The wizard is a wimp. At most, it can take two more of these wounds before dying or being reduced to a state of dying. The cleric heals this light wound and the wizard is fine. The fighter could take dozens of the same six by one wound and not be reduced to a state of dying. However, the cleric will have to patch up more light wounds on the fighter in order to get it back to a state where it has no gashes in it’s flesh. This is realistic, as the fighter has been gashed more times. In this way, a healing spell is a mechanic for closing wounds.

    Method 2: Percentage healing. The wizard has been gashed, six inches wide and one deep. While the gash is the same as the example above, the wizard has just taken a -serious- wound, not a light one, as it can only take two more hits like this before being reduced to a state of dying. The wizard is not being a wimp, he just isn’t as tough, so he needs a Cure Serious Wounds to get him back to fighting effectiveness. Meanwhile, the six inch gash barely hurts the fighter, and the same wound is closed with Cure Light Wounds. In this way, we think of healing as a mechanic of restoring someone to combat effectiveness. This makes no sense; a six inch gash could be closed on a fighter, but not a wizard, with Cure Light Wounds? Why? A fighter who has one wound closed up is not going to benefit as much as the wizard who had the same wound closed up? Why?

  5. MS Kati says:

    Hmm, looking back over my comments, they still aren’t very coherent. I’ll have to think about how to word it and try again.

  6. Elodie Hiras says:

    Myself, I use the D20 Modern third party sourcebook Blood and Guts 2, and all falls in place pretty well.

    Basically, if you take damage that’s neither a critical hit nor massive damage, it was just a grazing hit. You got bruised by the club, scratched by the sword, or the bullet struck you at an odd angle and left a minor wound. It hurts like hell though, but given that it was just a scratch, you just grit your teeth and take it. When you get in negative HP, you are in so much pain that you pass out, and start suffocating on your tongue or what have you. If you get hit again while you are stabilized, you get in shock and start suffocating again.

    If someone tries to slice your throat while you’re down, it’s called a Coup de Grace and you’re unlikely to survive it.

    Now, if you get hit by a critical hit or massive damage, you must make a fortitude save or suffer an injury. Injury depend on where you were hit (there are localization tables in Blood and Guts) and a random roll. Injuries require a Treat Injury skill check depending on the injury and getting harder for each hour teh injury was left untreated. If the check succeeds, the injury will heal given enough days, if not it becomes a permanent injury.

    If I play a campaign with magic, lesser restoration counts as an instant Treat Injury check with a bonus equal to the caster level, and restoration counts as an automatic success on a Treat injury Roll, and affects even permanent injuries.

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