A different take on falling damage

 It's always bothered me a little bit that falling damage in D&D is something that can be withstood by having more hit points. Sword blows, sure; hit points represent the skill and combat reflexes to turn potential killing strokes into glancing blows and superficial wounds. Arrows are a little trickier, but it's still possible to envision saving oneself from a shot to the heart with honed instincts and conditioned reflexes. Falling, though... gravity and inertia don't give a flying fork about how good a warrior you are. We all fall at 9.8 meters per second squared. There's a certain limit within which it's conceivable that a nimble and trained person can control his landing so as to distribute the force of impact to minimize injury, but if you're falling 50 feet, it's much less likely to make a difference whether you land gracefully or awkwardly.

It's possible to model something a bit more "realistic" without abandoning the essential 1d6-per-10'-fallen formula, just by tweaking how it's applied. Instead of summing all the dice, you take the two highest ones (or in the case of a 10' fall, the single die result) and multiply that by 10. This is the percentage of the character's maximum hit points lost. Round fractions up, and minimum damage is 1 point. Using this method, it's very unlikely for a previously uninjured character, at full hp, to die from a 10' fall. (Unless the character has a total maximum of only 1 or 2 hp, but such fragile characters will only survive the rigors of adventuring for their first level or two by being very, very cautious anyway. Game-mechanical safety nets can only do so much. A PC with a maximum of 3 hp will survive a fall that takes 60% of his max hp, 1.8, rounded to 2, with 1 hp remaining.)

The math is a little more complicated than the standard rule, but not extremely so. Take, for example, a character with 17 hp who suffers 40% hp loss in a fall. 10% of 17 is 1.7; just pop in a decimal point before the last digit. (Single-digit hp would be zero-point-something.) Multiply by the actual dice result (4, in this case) to get to 40%: 6.8 hp, rounded up to 7, and hey presto! The character has 10 hp remaining after impact. 

Notice that in falls of 20' or more, the range is 2-12 (20-120%) and the character will die on a total of 10 or higher, representing 100-120% of max hp. The odds of  this happening vary by the number of dice rolled, as follows (from anydice.com):

2d6 (20'): 16.67%

3d6 (30'): 35.65%

4d6 (40'): 52.16%

5d6 (50'): 65.16%

6d6 (60'): 74.93%

7d6 (70'): 82.08%

8d6 (80'): 87.25%

9d6 (90'): 90.96%

10d6 (100'): 93.60%

As you can see, the chance of being killed outright by a fall increases pretty rapidly, but it doesn't discriminate much at all between high-level and low-level characters. Even a level 2 magic-user has a chance to survive a 100-foot fall, and even a 10th-level fighter could break his neck taking a 20-foot tumble. If anything, the odds seem a bit generous for a fall onto a hard stone floor such as one might take as a default assumption in a dungeon, but this is a game after all, and one emphasizing heroic fantasy, so I don't think it's too far out-of-whack. It feels intuitively satisfying to me; if it doesn't to you, then it's probably not the right choice for your game, and you should keep using the original rule or whatever other house rule you prefer. 

Remember up above, I mentioned the possibility of a nimble character softening his landing, perhaps through a tuck-and-roll maneuver or other acrobatic technique. It's very easy to model this, providing a significant benefit for shorter falls while not degenerating into absurdity for long plummets. Simply allow the character to subtract his or her Dexterity bonus from one die. On a fall of 10' or 20', this is pretty big; it automatically will reduce the overall damage taken, and could allow the character to escape completely unscathed. In the case of higher falls, it may mitigate the damage and chance of dying somewhat. Imagine, for instance, a character with a Dex bonus of +2 falls 40 feet and rolls 6, 4, 2, and 1 on her d6s. The two highest dice add to 10, so that's a fatality, 100% of max hp. Deducting her Dex bonus from either of those dice, though, reduces the total to 8, or 80%, which means being really banged up but surviving the fall. In a similar fashion, you could add a Dexterity penalty to one die to increase the risk for clumsy characters, but I probably wouldn't do this; being the poor bastard with a -3 Dex penalty is already rough enough without the possibility of it contributing to your death from stumbling into a shallow pit.

Note, however, that falling damage is always expressed as a percentage of the character's maximum hp, which means the odds of dying from a fall may go up dramatically if the character is already injured and has less than max hp at the time of the fall. A fighter who's lost 60% of his maximum hit points could easily die from a 10' tumble into a pit trap at that point. Hey, adventuring is not for the faint of heart!

As stated above, a hard but flat stone floor is a reasonable default assumption, but the numbers can easily be modified for more or less forgiving substrates. A fall onto soft mud or a pile of straw could be represented by subtracting a pip or two from one or more dice, or by subtracting dice from the pool, e.g. a -1 die means a 10' fall onto such a surface causes no harm, and a 20' fall only requires a single d6, and so forth. Adding pips to the dice or dice to the pool can likewise be used to model harsher falls, such as landing on jagged or rough stone.

So, there it is. Does it add some welcome verisimilitude to an aspect of the game that was wildly unrealistic to the point of breaking suspension of disbelief, or is it too unforgiving to high-level characters who deserve some superheroic durability even outside combat? What say you?