Does this tweak to Jumping rules have any pitfalls or problematic interactions?

Question

My players and I were long ago accustomed to the D&D 3.5e ruleset, but now comfortably enjoy 5e's simplicity. Still, there are some rules that we preferred from the previous system that we felt was handled less satisfyingly in 5e. While it doesn't come up often, jumping is one of those rules. 5e's system is straightforward and easy to understand, but leads to guaranteed results with no chance of failure, and it is unintuitive to us that proficiency in Athletics doesn't in any way help jumping. Also, my players and I like rolling dice. For this reason, I have brought forward the 3.5e Jump rules:

When you jump a distance or a height, make an athletics check. A running jump travels a distance up to the result of the check in feet, and up to ¼ of the result in height. From a standing jump, the check's result is halved. The Champion’s Remarkable Athlete ability grants advantage on this check rather than an increase in distance. Multiplying effects like Step of the Wind and the Jump spell multiply the result of this check. For example, with an Athletics check result of 20, a running jump may travel up to 20 feet in distance and 5 feet in height, and a standing jump travels up to 10 feet in distance and 2 feet in height.

A running jump is defined, as in 5e, as 10 feet of movement in a straight line immediately prior to the jump.

In practice, this means that players declare where they intend on jumping to, roll the dice, and then see how far they make it. This uncertain result leads to jumps being seen as an actual hazard, which causes the party to consider backup plans and safety measures for certain perilous jumps rather than treating 10-foot holes as meaningless terrain features that any gnome can consistently clear.

Looking at the numbers, it seems like the expected value (EV) of rolling versus baseline 5e rules is similar or slightly lower (10.5 EV vs 10 base), with a greater difference felt by high Strength characters (13.5 EV vs 16 base) but proficiency in Athletics closes this gap (15.5 vs 16 at level 1, 18.5 vs 18 at level 9). Expertise in Athletics of course increases the EV beyond the base rules. These numbers seem perfectly reasonable to me.

Are there any potential pitfalls* with this house rule? Are there any interactions with other abilities or game effects that might become difficult to reconcile with this change?

*(pun intended, I won't lie to you)

Answer 1

Jumping is just much less reliable (and may produce weird results)

That's ultimately what this comes down to. Given how very bad missing a jump can be if you're jumping over something very deep...this can turn into a "Roll well or die" situation. And because jumping is now never reliable in how far you go, the risk gets much higher.

The 'practical' issue I could see coming up is that binding the number of feet you can jump to a d20 roll results in a very, very large swing in how long of a distance you can jump. If your Zero Str Wizard makes that Athletics check and rolls a 2, they may end up jumping a shorter distance than they could have stepped. Or you could have the absurdity of the massively physically fit Fighter only managing to jump 6', while the gangly, scrawny Wizard launches off into a massive 20' bound.

If you're okay with this...and with "Jumping" slotting into the same domain as, say, a Stealth check where it's possible for the high-Stealth Rogue to flub their check and do terribly, but the Barbarian rolls a 20...then go for it. I see no actual mechanical issues. Just the oddity of how dramatically something as straightforward as jumping can swing...it's usually something people are pretty consistent at--not something that swings by 20' depending on the attempt.

Partial Frame Challenge/Experience

This is just how I run things, and my players have generally been happy with it. Yours might not be because, as you said, you and your players like rolling dice.

As a general rule, I don't call for a skill check if something is not a challenge. A Rogue with Expertise in Stealth sneaking past some ordinary guards? I don't even ask them to roll.

IRL, people generally have a pretty reliable distance that they can jump. You could represent this by putting a 'floor' on a character's jump distance...a distance they can always jump without needing a check.

Personally, I set it that if your Str score says you can make that jump, you can make the jump. If you want to jump further than your Str score allows, make an Athletics check with a DC based on how hard I think it'd be to get that extra distance (I don't bind it directly to feet jumped--it's "did you make it or did you not?").

Perhaps, as a suggestion to balance the two...you could set a floor that a character can reliably jump half their Str score in feet. If they want to go further than that, make an Athletics check. If you want to keep it bound to feet...then either do it as-is, but keeping the Floor in place (so if you have Str 10, no proficiency, but roll a 1...you still jump 5 feet). Or maybe go "Floor plus half your Athletics check" if you want a more reliable increase from 'pushing it.'

Answer 2

The biggest issue I see with this rule is that the worst-case jump distance is pretty low. Characters with Strength < 12 and no Athletics proficiency might fail to jump across even a one-foot gap from a standstill, or a two-foot gap with a running start. At Strength < 10 you could even fail a one-foot running jump.

However, the obvious DM workaround is to simply not call for jump checks at all unless the distance or other circumstances (such as uneven or slippery ground) are such that the jump could plausibly fail. If the characters come across a one-foot gap in an otherwise level floor, just let them step over it.

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The other issue I see is that, conversely, the best-case jump distance with your rule is pretty high. The same Strength 10 character with no proficiency, who might fail to make it across a two-foot gap if they roll a nat 1, could also roll a lucky natural 20 for a 20-foot (6 meter) running jump. That's a pretty decent distance for a competitive long jump and way further than an average person could possibly jump in real life. (Characters with high Strength and proficiency bonuses can of course jump even further, even far enough to break world records. But that's an issue with the vanilla 5e jumping rules too.)

However, I don't really see that as game-breaking either, at least not unless your PCs find themselves in a long jump competition. But it does mean that jumping becomes a lot more luck-based than in normal 5e — which I guess is your intent anyway. If you and your players don't mind that, then I see no real reason not to try it.

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Ps. Both of the issues noted above arise from the simple fact that a d20 roll is rather "swingy". If you wanted to tame that swingyness a bit, you could replace the d20 with, say, d10 + 5. This would let "Joe Average" from earlier safely jump a comfortable 3 feet from a standstill, or 6 feet with a running start, with no risk of failure. And it would also trim the upper end of the range a bit to keep Joe from breaking any world records.

Of course, this would mean that you wouldn't be rolling "an athletics check" any more — but then, with no DC, is it really a standard ability check anyway? You could just say e.g. that your maximum running jump distance in feet is d10 + 5, plus any modifiers and bonuses that would apply to a Strength (Athletics) roll (including your Strength modifier and possible proficiency bonus), and it should be clear enough.

(Just for fun, I also checked a few other rolling options like 3d6 and 3d20-take-middle to see how they compare. All of them give the same average baseline running jump distance of 10.5 feet, but the d10 + 5 option is the least swingy of those, with the lowest standard deviation and the narrowest range of possible results. Of course, for even less randomness you could use e.g. d6 + 7, but I don't think that's the way you want to go.)