Welcome to GMs Corner. A new curated collection of opinion pieces from our local GMs.
Hello!
Welcome to the first installment of the GM’s Corner here at Dice Dungeons. This will be a section where we discuss GM things; from how to get over your anxiety as a first time GM to tips and tricks even pros can use.
This time, I have been specifically asked to talk about a subject that I am very passionate about, and have only seen discussed in one buried thread in some orphaned forum somewhere:
You are rolling your d100 rolls wrong.
Now, it’s probably not your fault; these things get passed on from GM to player, and then from player to other players… like some sort of transferable disease. Don’t understand what you’re doing wrong? Let me show you.
Ok, First off, I’m talking about rolling a percentile die along with a d10. If you’re rolling an actual d100, well, this discussion isn’t for you. Let’s look at our dice, shall we?
The d10 is a pretty common damage die used in various RPGs, ranging from a d20 system like Dungeons & Dragons to 2d6 systems like those using the Powered by the Apocalypse engine. Let’s go over what each side means when rolling it in this context, shall we?
Now, let’s take a look at the percentile die. This has a very similar numbering scheme to the d10, with one very important distinction: there is an additional 0 after each number. These are used to denote the zeroes, tens, and nineties place.
Now, you might be saying, “Uh, yea. Obviously. This is a dumb article written by a dumb-o”. Well, let’s just reserve that judgement until after this next bit, ok?
So, in order to get a d100 roll without using an enormous golf ball of a die, we roll a percentile die and a d10 and add the result, right?
For instance, this is 37.
And this is 82.
And this is 69. Nice.
But what, I ask you, would you call the following roll?
Every single person I know would call this roll a 50. You’re treating the 0 on the d10 as an actual 0. OK. So, then I ask of you, what is the following roll?
Well, that’s obviously a 7. You have 00 on the percentile, and a 7 on the d10. It can only be a 7. It sure as heck isn’t 107, right? Because that’s outside of the range of the d100 roll, right? Because a d100 roll is from 1-100, right?
Everything I’ve shown you so far is fine.
Or it would be, if it weren’t for one little thing…
You see, you cannot treat both the 0 on a d10 as a zero and the 00 on the percentile die as the ‘zero’s place marker’.
It works for the most part, sure. A 10 would be a 10 and 0 on the percentile and d10. Same works for 20, 30, etc…
But, dear friends, how do you roll a 100 this way?
Most people would say a 00 on the percentile and a 0 on the d10. BUT, given the facts I’ve just carefully laid out, that violates the rules you determine the rest of your rolls by. A 00-0 roll would, technically, be a straight up zero.
Instead of a 1-100 scale, you’ve made yourself a 0-99 scale.
“Oh God, you’re right! How could we have been so stupid? How can we possibly repair this travesty?!” you cry out. Well, I’m benevolent enough a GM that I wouldn’t destroy your world view if I didn’t have a better one to replace it with. And, honestly, it’s pretty simple:
TREAT THE d10 THE SAME WAY YOU’VE ALWAYS TREATED IT.
This way, everything works out perfectly. You can’t roll a zero; a 00-0 roll would be a 10. A 00-1 would be a 1. 90-0 is the coveted 100 roll. Sure, a 40-0 roll being a 50 isn’t immediately obvious, but this is the only internally consistent method I can see here.
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Maybe you don’t want to change. That’s fine; change is hard. But know, fellow GMs and players, that the method you’re using is invalid. You’re changing the rules for different cases.
In a world where consistency in rules and mechanics is required, why too wouldn’t it be required when rolling the dice?
99 comments
Except D10 percentage rolls are grouped in ten brackets of ten.
10-19 20-29, 30-39, 40-49, 50-59
60-69, 70-79, 80-89 90-99
The actual first bracket being 01-09 + 00-0 =100
You can’t roll 0% on a actual d100, neither can you on the above method. Generally though, you can treat a 00-0 as an auto failure in roll under systems.
another article says that the players handbook says that 0 + 00 is 100 (it should be 10) – it makes no sense
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 o f 70 and 1 is 71, and 00 and 0 is 100.
Since we are bringing math into this let’s think about probability. You’re basically rolling two 10 sided die and rolling one 10 sided die is a 1/10 chance to get any number so if you roll two together that’s 1/10 × 1/10 which amounts to a 1/100 chance of every given combination. So instead of making it more complicated on yourself and saying that 00-0 is a zero just let it be the only exception to the rule and make it 100. Correct me if I’m wrong.
Thanks for the ego post, I don’t care and will continue to do it the way I always have.
The claim at the end that the standard percentile dice method is “invalid” is over the top. I keep wondering if this article is a fool’s errand prank.
This alternative method is replacing one special rule having a one in a hundred probability (00 + 0 = 100) with another special rule having a one in ten probability (0 = 10).
The two methods otherwise have no difference. The probability of rolling any number between 1 and 100 remains one in a hundred.