Is there a consistent way to transfer skill checks between various d20 type systems?

In D&D 5e, for example, a precedent is set for difficulty of skill checks, where 10 is easy, 15 medium and so on (or something like that, I don't have the books in front of me)

Surely it's possible to take scenarios that are inspiring from one game and place them in another, but this has the potential for the GM to make a lot of human error. I'm okay with taking a lot of time to transfer rules and playtest, but I'm wondering if there is an empirical way, a measurable and verifiable way, to transfer skill checks from any d20 system to another d20 based system. The verifyibility would be that players of an approximate power level have the same statistical capacity for success when moving from one system to another.

Is there a format or formula to follow? Have any materials been written on "porting" these skill checks and scenes?

The answer does not have to cover everything, but I am looking for something I can read that gives guidelines.

As an example, say that I made a scene I liked a lot for D&D, and wanted to port it to a new group playing in a different system more or less verbatim.

Players scale a tall seaside spire to a Roc's nest. Every 2 in-world minutes, a massive wave sends the imbalanced structure shuddering, and the players have to make a DC16 save to hold on for dear life. 150 feet up, the players are confronted with a harpy and must succeed a DC14 wisdom save (or something, I don't have the book) in order to not throw themselves off the cliff.

What are some materials or resources that I can call upon to "port" said encounter to another system? Are there any workable rules or formulas, or is it simply too broad of a question? I feel like there should be some relation to the possible success rate in games that share the same dice. I would think (perhaps incorrectly) that there is a correlation between the statistical probability of success and the number of sides on the die.

  • \$\begingroup\$ I think you need to specify the two systems you have in mind. Otherwise this is likely to be "too broad". The two main problems are that systems other than D&D may not have "skill checks" in quite the same way, and what does "an approximate[ly equal] power level" mean? \$\endgroup\$ Aug 7, 2019 at 16:55
  • \$\begingroup\$ Yeah, you’ll have to be more specific. Contrary to common belief, not all games related to D&D that use a d20 are actually part of the specific D20 System family. D20 System only powered 3.x era D&D games and its offshoots. For example, 5th edition’s system is based around d20 dice, but it doesn’t use the D20 System. So this question isn’t specific enough yet to be answerable. \$\endgroup\$ Aug 7, 2019 at 17:01
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    \$\begingroup\$ 5e’s system is related to other D&Ds (including The D20 System), but it doesn’t share it directly with anything so it doesn’t have a separate name. It’s just “D&D 5th edition”. Each D&D iteration published after 2000 has a similar d20+adds vs target number, but they each have different ways of changing the odds, so conversion is nearly but not quite straightforward, and depends on the details of the specific games. \$\endgroup\$ Aug 7, 2019 at 17:38
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    \$\begingroup\$ Aside from that though, I think this might be fine tagged just [dungeons-and-dragons], if you’re just asking whether it’s possible to consistently convert between D&D editions in general. \$\endgroup\$ Aug 7, 2019 at 17:51
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    \$\begingroup\$ You may—or, given these comments, you may not—be interested in answers to this question. \$\endgroup\$ Aug 7, 2019 at 21:07

1 Answer 1


No In general

The problem is that skill checks didn't work exactly the same way writ large in any of the systems. A very small example is in 4e Skill Checks could also be handled by Complex checks. Those simply do not exist in 5e so there's no way to replicate them. If you go back far enough (for example 2e) the skill system didn't even work as you suggest with difficulty "classes" and 1e and Basic D&D didn't even have a skill system (but looking at the modules you will see these kinds of 'checks' typically using straight rolls or some other mechanism).


Ignoring those cases, it's in most cases reasonable to do the conversion about how you suggest: Convert the numeric to the class of the skill in the system (e.g. Easy is between 10 and 15 or whatever) then convert it back to it's equivalent in 5e. That should, approximately, give you the right feel... with another caveat:

Some of the system would presume more available magical aid than 5e. So, if the effect was "or die" and the system was 3e, then that wouldn't translate as well to 5e because 5e doesn't really expect players to die often, but 3e you could buy a scroll of Raise Dead at the corner store (okay, that's an exaggeration, but, the ultimate point stands).

TLDR: You will unfortunately have to translate all of the checks on a case-by-case basis looking at both the difficulty AND the consequences of a failure and adjust accordingly.

  • \$\begingroup\$ I understand the point about the consequences of failure, I really do, but I think for the purposes of my question we would have to assume "all other things (including magic scroll of resurrection availability) kept equal", just to narrow the scope. Definitely keep that part in your answer though, it certainly is something to be considered. \$\endgroup\$
    – user52772
    Aug 8, 2019 at 14:31
  • \$\begingroup\$ @TylerGubala I do not envy the person doing a "Total Conversion Mod" in that way, but, sure. Note, however, that the "raise dead" was an example. There may be cases where an effect could easily be reversed in the "source" system, but isn't even "a thing" in 5e. Particularly note that Dispel Magic in 5e is very limited in scope, but was not in 3e. \$\endgroup\$ Aug 8, 2019 at 14:39
  • \$\begingroup\$ Yeah my question could use reframing. I, admittedly, don't have enough experience to pick these things out. \$\endgroup\$
    – user52772
    Aug 8, 2019 at 14:41