# How to Read a d100 Dice Roll. Are you doing it wrong?

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?

LadySunami

Life is full of exceptions, letting 00-0 be 100 isn’t the end of the world.

People use the dice the way they do for a reason. It’s far more intuitive then your proposal.

D

Hello, I am hoping to help:

00+1=1%

00+9=9%

00+0=10%

10+0=20%

90+0=100%

Did I miss anything?

Also, in the D&D rule book I have it does not mention a 00-90 die. “Percentile dice, or d100, work a little differently. You generate a number between 1 and 100 by rolling the ten-sided die twice. The first roll gives the tens digit, and the second gives the ones digit. If you roll a 7 and a 1, for example, the number rolled is 71. Two 0s represent 100.”

Milferd Jones

I played D&D in 1978. So this easy gas pumps mechanics only had two digits when price hit a dollar they painted a one to the left because it could calculate but no dispay three digits. Car Odometers only had five digits. So at 100,000 miles it read 00,000. It rolled over. Point being you got confused making a 00-90 dice that did not exist back then. Treat each dice as a number in a display and thus 00 has to be 100 as it can’t be zero. Normally we used two ten sizers of different colors.

Poopoo

ON THE OFFICIAL DUNGEONS AND DRAGONS BOOK, DUNGEON MASTER’S GUIDE, IT LISTS ZERO AS A NUMBER ON THE D100. LOOK AT PAGES 144-149.

Scott

Adding unnecessary math. And now you got 00 being 0 and 0 being 10. Bad system. The old way of the tens die and single die representing the tens place and single respectively, with 00-0 being the only exception, is much easier, and do not require unnecessary addition(no matter how simple) to the equation.