I run a B/X game for a few guys, most of whom have only played 3E before. It leads to a lot of talk about the change in power level between basic and 3E. One of the things that came up was the somewhat lower attribute modifiers and bonuses.

"Oh man!" I exclaimed. "I bet you guys don't know about percentile strength!"

So, I pulled up the 1E PHB and I was blown away myself to see just how much more powerful 18/00 was compared to plain old 18. A cleric with 18 strength gets +2 damage, while a fighter with 18/00 gets +6. Wow! I remember loving the extra roll being a possibility as a player, and hating the possibility for such a massive bonus as a DM. I don't think it ever came up in play, either way.

Where did this system come from? Was it just invented for AD&D 1E, or was it prefigured in a Dragon article, or what?

UPDATE: Given that aramis pointed out its origin in OD&D's Greyhawk, I doubt we'll find anything on the motivation for it, but if anyone finds that, I would still be quite interested. (Speculation like "Gary wanted to give more damage bonus to strong character" can be omitted, unless we find evidence.)


2 Answers 2


The first rulebook including it was D&D Supplement 1: Greyhawk, on page 7. This predates AD&D by several years.

It also places it squarely into Gygax's purview.


Gygax answered that questions many times. Here is the first one Google found for me.

At first blush I decided that 18 was the maximum for a human, but then to make fighters more viable, and because the concpt of degrees of strength in the 18 cap followed logically, I used the percentile measurement. As for strength over 18, any such ability is superhuman and must be magically endowed in my view. The 18/% did give the fighter a real boost.

To the best of my recollection, I have never suggested percentile breakdown for stats other than strength.

Although, when Gary published the Cavalier class in Dragon #72, he did give them percentile values for dexterity and constitution as well. Although this was more about tracking improvements to the scores rather than to provide extended modifiers between 18 and 19 like exceptional strength.

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    \$\begingroup\$ I would love to know why he felt that percentile measurement "logically followed" 18. I kind of see why simply going to 19 was rejected, but since 18/00 seems much better than 19 or 20 would have been, the claim that it's lesser seems to be almost farcical. \$\endgroup\$
    – KRyan
    Commented Mar 24, 2015 at 16:50
  • \$\begingroup\$ To that I can only guess. I think he was thinking that the curve was asymptotic to 19; it would never get to 19. (I don’t think we saw higher scores until the belts of giant strength in the DMG? Except that the PHB allows a Con of 19.) So, to give numbers to the ever rarer points between 18 and 19 meant using fractions. Decimal fractions would be good and would allow distinguishing the top 1%, the top 9%, the top 25%, and the top 50%. And they can be easily generated with d%. And if you’re rolling the d%, just put 18/% rather than converting 00 to 18.99, etc. \$\endgroup\$ Commented Mar 24, 2015 at 18:18
  • \$\begingroup\$ Probably the logic was in the sense that one might talk about "upper quartiles" or the "top 1%". It's worth remembering that the original 18/50 score was in fact no different from a straight 18, so half of even 18 STR fighters did not in fact enjoy any bonus. I prefer that to the AD&D version, but not enough to bother players with a house rule on the subject. \$\endgroup\$
    – Nagora
    Commented Mar 24, 2015 at 18:25
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    \$\begingroup\$ It also occurs to me that a guy in Gary’s 2005 oD&D campaign said that he used roll-under ability score checks. (Can’t find the DF thread at the moment.) If he was doing that in the ’70s, that might explain his reluctance to let Str scores go above 18. \$\endgroup\$ Commented Mar 24, 2015 at 19:01
  • \$\begingroup\$ Found it. It wasn’t Deogolf, it was Col_Pladoh himself 3d6 ability score checks \$\endgroup\$ Commented Mar 24, 2015 at 19:13

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