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I recently had a discussion with someone about d100, specifically the two ways of reading the slightly specialized pair of d10s typically used for the purpose. As context for anyone unaware, a normal d10 shows the numbers 0-9 but the 0 is treated as 10. The second d10 in the pair has an additional 0 on each face, showing 00-90 in increments of 10.

In theory there are many ways to use these two dice to generate a number from 1-100, but only two that are generally considered reasonable:

  • The two-digit die tells you the 10s place of the result, the one-digit die tells you the 1s place of the result. 100 is the number in the desired range which has a 0 in both 1s and 10s places, so dice showing "00" and "0" is 100.
  • The normal d10 is rolled as a normal d10, and the other die is rolled as-written giving a number from 0-90; the two dice are then added together. "00" and "0" are then equal to 0 + 10 = 10. This method of rolling is particularly intuitive when the normal d10 is actually marked 1-10, but particularly unintuitive if you were to lack a special 10s die and were trying to roll on two dice both marked 1-10.

Based on this and similar questions, it seems that treating 00+0 as 100 is the more traditional option, with some tables in older editions explicitly marking 00 rather than 100 on their tables, but I only knew that for sure because I had experience with prior editions. I expect D&D 5e has specific guidance on what the "dX" dice notation means, which would probably indicate how d100 should be rolled, but where is it?

NotArch
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Kamil Drakari
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  • If you'd like to bounty the duplicate or submit your answer there, that would be fine. – NotArch Jun 01 '21 at 19:31
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    @NautArch The question marked as a duplicate does not restrict itself to D&D 5e, nor do any of the answers cite D&D 5e material as evidence. The more recent question I already linked is a better duplicate target, since at least one of the answers has the information I had been looking for (though not the accepted one). – Kamil Drakari Jun 01 '21 at 19:36
  • @NautArch: While the self-answer below could be a valid answer to the earlier question (at least with small changes, like appending "for D&D 5e" to the heading), this question and its answer also seem like a perfectly valid Q&A pair to me. Given a general system-agnostic question on "how to do X" with several different correct answers, a follow-up question on "what is the officially recommended way to do X in system Y" seems perfectly reasonable to me. Voting to reopen. – Ilmari Karonen Jun 01 '21 at 20:42

1 Answers1

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00 + 0 = 100 is official

Both the Player's Handbook and the free Basic Rules have a section in the Introduction which describes how dice work in general, what the "dX" notation means, and specifically how to use two ten-sided dice to simulate a d100. Both sections on d100 are identical:

Percentile dice, or d100, work a little differently. You generate a number between 1 and 100 by rolling two different ten-sided dice numbered from 0 to 9. One die (designated before you roll) gives the tens digit, and the other gives the ones digit. If you roll a 7 and a 1, for example, the number rolled is 71. Two 0s represent 100. Some ten-sided dice are numbered in tens (00, 10, 20, and so on), making it easier to distinguish the tens digit from the ones digit. In this case, a roll of 70 and 1 is 71, and 00 and 0 is 100.

I will note, the section does not offer any advice on what to do for d100 if some or all of your ten-sided dice are instead marked 1-10, and it also doesn't clarify how to roll a normal d10 if all your ten-sided dice are marked 0-9.

Kamil Drakari
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