5e: Stamina Check Variant Rule (Take 2)

This post was updated on 04/02/2019 to reflect changes to the house rule based on feedback received. 

I've got the results of a random thought experiment for you today: what if when you level you roll an ability check to determine hit points gained? With no skills tied to the Constitution ability score, very few constitution checks ever happen in the game (concentration checks aside, most constitution-based rolls are saving throws). This proposed rule would give you new reasons to roll a Constitution check: whenever you gain hit points upon leveling, and whenever you want to spend a Hit Die.

Stamina Checks

This house rule replaces rolling Hit Dice with an ability check. The results don't map exactly to traditional Hit Dice rolls as it's impossible to perfectly replicate those odds using an ability check, but a character should still find their hit point rolls competitive, and often better. As a character's proficiency grows, their results become even more favourable, particularly if they're in a class which multiplies the proficiency bonus to the check.

You roll a Stamina Check when you gain hit points upon leveling up, adding the result to your hit point maximum. Instead of gaining Hit Dice to spend on healing during a Short or Long Rest, you gain Stamina Points. During your rest you can spend Stamina Points in the same way you would have spent your Hit Dice. Each Stamina Point spent lets you roll one Stamina Check and recover hit points equal to the result. As you would have done with Hit Dice, keep a separate pool of Stamina Points for each class a multiclass character possesses. When you spend a Stamina Point from one of your classes, the bonus you receive to your check is determined by that class. Once again, the results will tend to favour the PCs at higher levels, making their natural healing more effective.

At the DM's option, they can also call for a Stamina check whenever a character is attempting a feat of endurance, rather than simply calling for an untrained Constitution ability check.

Summary

Here's how Stamina checks work:

• A Stamina check is a constitution ability check. Your class determines whether you have proficiency or expertise on the roll, as shown on the Stamina Check Modifiers table. 
• Your result determines the number of hit points you gain, as shown on the Stamina Check Results table. 
• You don't add your Constitution bonus to your Hit Points. Instead, your Con modifier has been factored in to the check itself. Note that this does mean that using this house rule, a character's Constitution bonus doesn't translate to hit points on a 1-to-1 basis. It's still important, but doesn't weight your result quite as significantly. Each +1 to Con effectively becomes a +0.5 to hit points. However, the proficiency bonus and the weighting of the results table pick up that slack. 
• Optionally, if the DM allows you to take the average result and you wish to do so you can treat the result as though you had rolled a 10 and added all your modifiers (eg. a passive check/Take 10). 

The formula used for the Check Results table is hit points = ability check result / 2. It's impossible to perfectly simulate the same spread of results as standard hit dice, so the important thing is for the formula to hew as closely as possible, erring on the side of generosity. A consequence of this is that characters sometimes get more hit points than would be possible in the normal rules, so before implementing this house rule be aware that characters may end up being more resilient and heroic, especially as they gain levels and the influence of their proficiency bonus on the check rises.

Stamina Check
Modifiers

Class (HD)	Modifier
Sorcerer/Wizard (d6)	You add your proficiency bonus -2 to the stamina check.
Bard/Cleric/Druid/Monk/Rogue/Warlock (d8)	You add your proficiency bonus to the stamina check.
Fighter/Paladin/Ranger (d10)	You have expertise, allowing you to double your proficiency bonus to the stamina check.
Barbarian (d12)	You triple your proficiency bonus to the stamina check.

Stamina Check
Results

d20 Roll	Hit Points		d20 Roll	Hit Points		d20 Roll	Hit Points
0	0		15	8		30	15
1	1		16	8		31	16
2	1		17	9		32	16
3	2		18	9		33	17
4	2		19	10		34	17
5	3		20	10		35	18
6	3		21	11		36	18
7	4		22	11		37	19
8	4		23	12		38	19
9	5		24	12		39	20
10	5		25	13		40	20
11	6		26	13		41	21
12	6		27	14		42	21
13	7		28	14		43	22
14	7		29	15		44	22
						45	23

Examples

Let's take a look at some of the possible results:

• d6 Class (using a +0 Con Wizard as an example):
• A 2nd level wizard with 0 con can get a result between 1 and 20. Their hit point range is between 1 and 10. They gain 5 hit points if they use an average/passive check instead of rolling.
• At 5th level, the wizard's possible results are between 2 - 21. The minimum hit point floor remains 1 (albeit with less likelihood), but their maximum and average increase by +1. 
• At 9th level, the wizard's potential results are 3 - 22. The minimum hit point floor increases to 2, while their maximum and average remain the same, though with increased likelihood of achieving those numbers.
• The pattern repeats at 13th and 17th level, increasing the wizard's minimum and maximum results by +1 each time. By 17th level, the wizard's possible results are 5 - 24. Their hit point range is  3 - 12. They gain 7 hit points if they use a passive check instead of rolling.
• d8 Class (using a +0 Con Bard as an example):
• A bard's progression is very similar to a wizard's, except their minimum, average, and maximum stamina check results are all higher by +2. This means that their minimum, maximum, and average hit points at any level are 1 higher.  At 1st level their hit point range is  2 - 11, and they gain 6 hit points if they use a passive check instead of rolling. By 17th level, the bard's hit point range is  4 - 13, with a passive check of 8. 
• d10 Class (Using a +0 Con Fighter an example):
• A 2nd level fighter can get a result between 5 - 24. Their hit point range is  3 - 12. They gain 7 hit points if they use a passive check instead of rolling.
• At 5th level, the fighter's possible results are between 7 - 26. Their  minimum, maximum, and average hit points all increase by +1. 
• At 9th level, the fighter can achieve results of 9 - 28, increasing their minimum, maximum, and average hit points by a further +1.
• The above pattern repeats at 13th and 17th level, increasing the fighter's minimum and maximum results by +2 each time. By 17th level, the fighter can achieve results of  13 - 32. Their hit point range is 7 - 16. They gain 11 hit points is they use a passive check instead of rolling.
• d12 Class (Using a +0 Con Barbarian an example, however unlikely!):
• A 2nd level barbarian can get a result between 7 - 26. Their hit point range is  4 - 13. They gain 8 hit points if they use a passive check instead of rolling.
• At 5th level, the barbarian's possible results are between 10 - 29. Their minimum hit points increases by +1, while their  maximum, and average hit points both increase by +2. 
• At 9th level, the barbarian can achieve results of 13 - 32, increasing their minimum hit points by +2, while their maximum and average hit points increase by +1.
• The above pattern repeats at 13th and 17th level, increasing the barbarian's minimum and maximum results by +3 each time. By 17th level, the barbarian can achieve results of  19 - 38. Their hit point range is 10 - 19. They gain 14 hit points is they use a passive check instead of rolling.
• Characters with Constitution bonuses:
• Refer to the examples above, but: 
• Each +1 to Constitution increases the minimum and maximum floor of the results by +1.
• A +1 to Constitution is effectively worth half a hit point. The proficiency progression of the Bard example shows what happens when a character gains an additional +1 to their result. Depending on the character's level, it either increases the average and maximum hit points by +1, or increases the minimum hit points by +1. 
• Each +2 to Constitution is guaranteed ot increase the character's minimum, maximum, and average hit points by 1. 

Consequences & Implementation

A house rule can have wide-reaching consequences, particularly when it alters something as mechanically fundamental as hit points. These impacts should be considered carefully, and the advantages and disadvantages to your game weighed before implementing the rule. What seems like a worthwhile trade for one game may not be a good fit for another.

Stamina checks change the game in the following ways:

• On average, a PC should end up with higher hit points than they would normally have (the difference should be negligible at low level, lucky rolls aside, but more noticeable at higher levels. Because hit points are based purely on the check result and there are no caps by class, PCs can gain hit points in excess of the the limits imposed by the normal rules (or at least, defying the probability of their possessing enough Constitution to get such a result under the normal rules). A 2nd level wizard, for instance, could roll luckily and add 10 hit points to their maximum!
• There are similar consequences to natural healing on a Short or Long Rest, with the average amount of hit points recovered per Stamina Point exceeding the average for Hit Die + Con. 
• Warrior classes (d10 and d12 Hit Die) benefit the most from the house rule, since they double or triple their proficiency score respectively. This extra buffer is comparatively greater than the gains of less combat-oriented classes, particularly at higher levels where the multiplier to proficiency makes a significant difference.
• The value of a character's Constitution is slightly diluted. Normally, +1 Constitution = + 1 hit point. When using Stamina checks, +1 Constitution = +0.5 hit points. This is an unavoidable consequence of using an ability check. A high Constitution score is still worthwhile, but players may feel it is less of a priority. If they so wish, the DM can increase the value of Constitution again by making an active effort to increase the number of Constitution ability checks and saving throws they ask their players to make.  

The overall effect of Stamina checks is to make characters more resilient, which is either an advantage or a disadvantage depending on how heroic you like your player characters to be: bigger pools of hit points and improved short rest healing will make the party tougher on the whole (though they must still protect their squishier casters). High level warriors who might feel a little underwhelming compared to casters who are capable of mind- and reality-bending spells are certain to appreciate their additional potency. You can pull out the stops to Go Big with gonzo action.

If you like the idea of Stamina checks but would rather the characters gain hit points that are still in line with the possible ranges of the core game, here are a few variants you could consider:

Implement the house rule but enforce passive checks at level up. 

Players don't roll to increase their hit point maximum, they always add their modifier to 10. This should result in hit points that are comparable or better than the standard rules, but do remain within the game's expected ranges. To take the most extreme example I can think of, a 20th level Barbarian with 24 Con:

• With Hit Dice, their average hit point result at 20th level is 14 (7 + 7 Con). They could attain up to 19 hit points (12 + 7 Con). 
• Using Stamina Checks, the barbarian's passive Check would be 35 (10 + 18 proficiency + 7 Con), resulting in 18 hit points. This is considerably better than a barbarian's normal average, but remains within the expected range of possible outcomes. 

Static Bonuses to proficiency, not multipliers.

d10 and d12 classes don't multiply their proficiency bonus. Instead, a d10 class adds its proficiency +2 to their roll. The +2 bonus amounts to +1 hit point compared to a d8 class. A d12 class adds its proficiency +4, or in other words +2 hit points.

Take 2 Changes

A previous version of this article used the formula hit points = ability check result / 2.5, rounded to the nearest whole number. I settled on this formula because it provided the correct average hit points for a character with +0 Con, but I had missed that it broke down at higher check modifiers and could leave characters with underwhelming average hit points compared to the default system. Thanks to reader J for pointing this out. 

A more generous formula of hit points = ability check result / 2 solves the issue, while simultaneously helping offset the difference caused by the reduced contribution of a character's Constitution bonus to their hit point total. It can, if anything, be too generous, but as discussed in the article that's a cost/benefit analysis each DM can make for themselves! 

As part of the overhaul, Barbarians now triple their proficiency bonus rather than adding advantage as previous. Advantage interacts strangely with the system in that it has very different consequences depending on whether you roll it or add +5 to a passive roll to get your average. It's fairer and cleaner for a Barbarian player to get the same benefits in either situation. 

Closing Thoughts

I really like this house rule and I think I'll try it out for my next game. If you use it, let me know how it goes for you!