House Rules for Moldvay Basic

Let's say you started a new D&D game by getting the 1981 Moldvay Basic D&D Rulebook and making that available to all of your players (for example, by way of the new DnDClassic.com website, at which it's currently the best-selling item and the only core rulebook available, for argument's sake).

Now, if it were me, I wouldn't run those rules precisely as published, but I'd attach a few well-considered house rules. Fortunately, there's not much work to do: my Original Edition Delta house rules, although written with OD&D in mind, are perfectly suitable for the exact same purpose in the case of Moldvay. In fact, in several cases, my house rules are actually more compatible with Moldvay than they are with OD&D Vol-1, because: (a) we both incorporate selected parts of the OD&D Greyhawk supplement, and (b) we both agree on the necessity of certain edits to matters of scale & time. (Remember: you can download the OED house rules for free from the OEDGames.com website, as shown in the sidebar here.)

I recently dug out my very beaten-up copy of the Moldvay Basic D&D rules just to check in on where we agree and disagree on the best practices for the game. Here's a "Top 5" list of stuff that we agree on as needing to be changed from OD&D:
  1. Class hit dice are as given in the Greyhawk supplement (Fighters get 1d8 every level, and Magic-Users get 1d4 every level; although I differ in giving Thieves 1d6 per level). 
  2. Variable weapon damage from the Greyhawk supplement is used, but we both strip out the complicating "L-size" category of damage.
  3. Experience awards from monsters are given by a geometric scale, also taken from the Greyhawk supplement (in the past I used the linear system in Vol-1, but I've since been convinced that Greyhawk really is better). 
  4. Miniature combat scale of 1"=5' is seen as necessary (Moldvay p. 61), as opposed to OD&D's 1"=10' or AD&D's often-forgotten 1"=3⅓' scale.
  5. Time scale really should be 1 round = 10 seconds (Moldvay p. 15, 23), as opposed to OD&D or AD&D's nutty assertion that 1 round = 1 minute.
But here's a "Top 5" list of stuff that I do differently from Moldvay:
  1. Class & race will be separate considerations, as in OD&D/AD&D; and clerics will be deleted, as usual for me. This leaves only the class tables for Fighters, Thieves, and Magic-Users. Elves will split their XP between the Fighter and Magic-User classes (and I do this by having them select one of those classes to get the XP before an adventure begins).
  2. I don't give the ±3 modifier at ability scores of 3 or 18, which Moldvay introduced. My feeling is (a) that's frankly too large a bonus for the scale of the system, and (b) it's better to have a pattern that you can continually scale upwards, i.e.: 13-15 is +1, 16-18 is +2, 19-21 is +3, 22-24 is +4, etc.
  3. Money will be according to a silver standard; encumbrance is tracked in stone units; and attack resolution is done by the no-lookups-necessary "Target 20" system (roll d20+level+AC >= 20; see the sidebar).
  4. Spell durations I measure as if 1 turn = 1 minute (same as the original Chainmail turn scale), not by the 1 turn = 10 minutes rule established in OD&D Vol-3 and carried throughout the rest of the Basic and AD&D lines.
  5. Monster hit dice and damage will all be 6-sided (as it was in OD&D pre-Greyhawk; so much simpler for the DM to roll!)

There are other minor alterations, such as: I give Fighters a feat every 4th level (I consider that a generalization of AD&D features like exceptional strength and weapon specialization), I don't allow lamp oil to be lit on fire in a pool (Moldvay actually gives a uniquely generous allowance for that; p. 26), etc. But Moldvay really does a lot of great stuff, and if a bunch of people started playing with his version of the Classic D&D rules, then I think that would be an immensely rewarding vein to be mined.

If you haven't yet seen Moldvay's version of the D&D rules (you should!), you can use the following affiliate link to get it (and help support the Wandering DMs channel at the same time):

Moldvay's Basic D&D at DriveThruRPG


  1. That is interesting. I actually got my start with Moldvay, so it has been my baseline. I'm curious about your Target 20 system. Does that mean that heavily armored fighters (AC 2 or so) have less of a chance to hit than a thief (AC 7 or so) or a magic-user?

    I was just re-reading last night the thread about a Holmes-only campaign and am presently working on a Moldvay-only campaign with as few changes as possible, but all of your suggestions look good. Keep up the good work!

  2. Oh crap. I get the AC thing now. I'm an idiot. In my defense, I haven't had any coffee yet.

    1. The best thing is when someone answers their own question, saves me from writing up the reply. So thank you! :-)

  3. Couple things ...

    How do you use 1" = 5' when three characters fight side-by-side in a 10' corridor?

    A +3 bonus only changes a failure to success 1/6th of the time. That doesn't seem too extreme. In fact, when dealing with contests of stat vs stat it's not quite enough.

    How do you use spells lasting a few minutes when time is measured in turns? Spells like Light or Tenser's Floating Disk become all but useless.

    1. I do generally limit fighting in a corridor to just 2 characters. This is consistent with the AD&D space required stats for weapons like broadswords, battle axes, and maces.

      Some spells might indeed need modifications. Light is usable within a combat, in case something extinguishes your normal lights, you get immersed in water, etc. (for longer usage get the 2nd level spell). Tenser's Disc isn't in my OD&D game, so I hadn't dealt with it; probably need to increase that to some hours or a day.

    2. I was surprised to see OD&D allowed 3 men to fight abreast. I noticed that when I was looking for another unrelated rule. I thought we played that way because some old computer game did it. EPT lists which weapons allow 3 vs 2. I like that as it gives a benefit to spears and short swords which otherwise are never picked.

  4. "Delta house rules" has a whole other meaning to fans of the film Animal House...!