The Percentage Damage Rule
There has always been much controversy over the realism of hit points in D&D, with regards to why a 9th level fighter receives only a scratch from a sword thrust while a 1st level fighter may be skewed by one. According to many sources, the answer to this is that, as the character rises in level, his hide does not become physically tougher, but his skill in combat improves to an extent whereby he is able to avoid the full brunt of a blow which may have felled a less experienced victim. This is considered fairly believable to players, and no more is said – until, that is, the character becomes wounded in a non-melee instance.
So why does a character with 80 hit points fall down a 10 foot pit and merely bruise himself, while one with 4 hit points breaks his neck? Perhaps the higher level adventurer is more proficient at falling down pits and landing properly – hardly likely I think, considering it takes a mere 0.6 seconds to fall that 10 feet – or perhaps his skin and bones are physically tougher, which is even less likely. A DM in this situation is stuck for a reasonable answer.
Another point that comes to mind is the relation between hit points and missile fire. Why does that arrow only do 1-6 points of damage, capable of killing a normal man instantly, but requiring some dozen arrows to affect any medium level adventurer in the same way, so that the latter eventually walks around resembling a porcupine? Well, the answer to this (and the only answer with a touch of reason in it that I can think of) is that the higher level character can dodge the missile to some extent so he only receives a glancing blow. But what about when he’s surprised or shot at from behind? – that arrow’s still going to do that 1-6 damage, still barely scathing him. Mmm – the DM is stuck once again.
To try and set these problems right to some extent, I have developed a rule for damage sustained during missile combat and non-melee situations. The rule is ‘The Percentage Damage Rule’. That is, damage taken via the aforementioned is a percentage of the character’s original hit points. Damage sustained is rolled first on a d100 and then cross referenced on the table below depending on the missile type. Then the following formula is applied:
Damage sustained = original number of hit points x percentage damage
100
Example 1:
A 10th level dwarf fighter has 80 hit points. While he is strolling along a street, he is surprised by an elven archer who fires at him from a balcony 30 feet above the ground. The elf player rolls an 18 to hit, with no adjustments for range, and easily hits the dwarf’s AC4. The elf player then rolls a D100, and rolls a score of 53. This result is cross-referenced on the table against "Arrow", and the player finds that the dwarf has sustained 40% damage.
Thus: Damage sustained = original number of hit points x percentage damage = 80 x 40 = 32
100 100
So, the dwarf takes 32 points of damage.
Example 2:
A 3rd level magic-user has 8 hit points, but sustained 3hp of damage in a recent fray, so he only has 5hp left. Rounding a corner the party of adventurers encounter a tribe of orcs. The orcs, gaining initiative, opt to discharge their spears at the party. One of the spears strikes the magic-user and easily penetrates his paltry AC10. The DM rolls a D100, and gains 84. Cross-referencing this against "Spear" on the table shows that the magic-user sustains 80% damage.
Thus: Damage sustained = original number of hit points x percentage damage = 8 x 80 = 6.4
100
The magic-user takes 6.4 damage, rounded down to the nearest whole number, which equals 6hp of damage. However, he only has 5hp left, so is killed outright.
Percentage Damage Taken (roll D100)
| WEAPON | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% | 100% |
| Arrow | 1-10 | 11-20 | 21-50 | 51-60 | 61-70 | 71-80 | 81-85 | 86-90 | 91-95 | 96-00 |
| Dagger | 1-30 | 31-60 | 61-70 | 71-80 | 81-85 | 86-89 | 90-94 | 95-97 | 98-99 | 00 |
| Dart | 1-50 | 51-80 | 81-85 | 86-90 | 91-93 | 94-96 | 97-98 | 99 | 00 | - |
| Javelin | 1-10 | 11-20 | 21-40 | 41-60 | 61-70 | 71-80 | 81-85 | 86-89 | 90-94 | 95-00 |
| Quarrel (heavy) | 1-20 | 21-40 | 41-60 | 61-70 | 71-80 | 81-85 | 86-89 | 90-94 | 95-98 | 99-00 |
| Quarrel (light) | 1-30 | 31-60 | 61-70 | 71-80 | 81-85 | 86-89 | 90-94 | 95-97 | 98-99 | 00 |
| Sling (bullet) | 1-20 | 21-40 | 41-60 | 61-70 | 71-80 | 81-85 | 86-90 | 91-94 | 95-98 | 99-00 |
| Sling (stone) | 1-30 | 31-60 | 61-70 | 71-80 | 81-85 | 86-89 | 90-94 | 95-97 | 98-99 | 00 |
| Spear | 1-10 | 11-20 | 21-40 | 41-60 | 61-70 | 71-76 | 77-82 | 83-88 | 89-94 | 95-00 |
| OTHER | ||||||||||
| 10' pit | 1-10 | 11-20 | 21-40 | 41-60 | 61-70 | 71-76 | 77-82 | 83-88 | 89-94 | 95-00 |
(+10% per 10' thereafter)
Magic Weapons
For magic weapons and arrows/quarrels add +5% for each +1 of the weapon to the die role before cross-referencing the table. Magic bows and arrows are cumulative, so a +1 bow with a +3 arrow, add +20% to the role.
Monsters
It should be noted that this rule applies to PCs and NPCs who have to ability to rise in level. It does not apply to monsters whose hit points are calculated based on the toughness and size of the monster.
Obviously, this rule will be harsh on players and NPCs alike, increasing damage sustained in non-melee means to a great extent. Players will find the resulting damage astounding in comparison with that original harmless 10' pit trap. However, I feel that if you persevere and bother to use the formula they will eventually agree that it is a much fairer and more realistic method of determining damage, even if soul-destroying! My AD&D group have been using the Percentage Damage Rule for the past 15 years and everybody agrees it makes the game much more realistic. It certainly stops high level PCs from mindlessly charging an archer with a fully loaded crossbow!
Please feel free to email me if you have any comments or suggestions regarding this article.