Contemplating Percentages.

Talking about random number generation from 1-100. There are multiple ways to achieve the same results. Some are easier to use than others.

Let’s discuss some different ways dice can emulate a span of 1-100 as it comes up in RolePlaying Games.

Different games have different die types and rolling conventions, but it all still comes down to a span of numbers 0-100. We’ve had various physical dice through the years, but they all do basically the same thing.

In the stone ages of miniatures wargaming, in the before time- 1970, when dinosaurs walked the Earth and people listened to disco music, we had twenty sided dice numbered 0-9 twice. First roll is first digit. Second roll is second digit. Good to go, right?

Then came our friend in dice, the d10. Roll it twice. Once for the first digit, second time for the second digit. Done. Easy mode.

My gaming group for Marvel Superheroes RPG used to roll two dice and call the color of the first digit. I had a player (Travis) who liked to change up the color of the first digit die. This led to way more hits than misses.

Then came the argument over whether or not the result of 00 + 0 was to be read as 0 or 100. One is usually a catastrophic hit or a horrid miss depending on the system. Don’t look it up on the Internet. We can’t decide on there, either. I leave it to the individual GM to decide. Depending on the game we either roll between 1 and 100 or 0-99. Either way, game on.

Another way a wise friend once explained it, is EVERY d20 based game functions on percentages. 1d20 x 5 = a span between 5 and 100. Oh looky, percentages.

That’s a 60. I called Yellow first.

Then, someone in the glorious 1980s made a miracle die- the d00, or double-digit ten sider. I love these dice for percentages. No more arguments over which die went first. The d00 always determines the first digit. Easy.

The mighty Zocchihedron!

There’s one die I haven’t mentioned. Everyone’s favorite golf ball, the Zocchihedron, an actual 100 sided die. One roll and done.

Through years of working in the game industry, I’ve also seen d50s and d100s that look like gigantic ten sided dice. The only downer is many of these dice are hard to read. (Sorry, no pics on these as I don’t own any.)

There are also digital 00-99 counters that offer up a new number at the push of a button. I haven’t seen any lately, but I know they’re out there. I hear they’re cool. Obviously we all have dice phone apps and office applications capable of generating random percentages, but what fun is that?

We could potentially oversimplify the whole process and roll 1d10 x 10 or the d00 by itself. We’re just omitting that pesky second digit. Oh well. All good, yes?

Okay, cool math rocks, but why are we here?

I’m still working on my own TTRPG engine that is theoretically going to cover Fantasy, Cyberpunk, AND Mecha Starship Sci Fi. I cut my teeth on Cyberpunk 2020, Mekton Z, Rifts, and Robotech back in the early days. Of course I also ran a lot of Marvel Superheroes and AD&D Basic-2E AD&D. I’ve called for my share of percentage rolls. I’ve seen the mighty d20 at the best and worst of moments.

It’s all about the manipulation of probability. A +1 to a d20 roll is the same as 5% A +1 to a d00 roll (both 1d00 + 1d10) is a drop in the bucket at a paltry 1%. However, a +1 to a 1d10 roll gets you a 10% bonus, and that’s pretty good.

I want a system where a +1 bonus really means something again. I’ve noticed a tendency for a lot of d20 based games to hand +1 bonuses out like parade candy. What I intend to do instead is have a 1d10 based system where skill really counts. So the base roll in my system will be 1d10 + Attribute OR Skill level vs target number. The higher the target, the tougher the challenge is to beat.

That’s how skills and combat will likely work. I’m also bringing back my beloved AD&D 2E initiative system since it ran on a 1d10 roll with bonuses/penalties. Of course, there will still be times when the d00 is rolled. We’ll also discuss warping of percentages by using dice cleanly indivisible into 100. (In other words, there is no way to get a d6 or a d8 to emulated a 1-100 chance without crunching some more serious math.

Thanks for being here. In the next article from this series, we’ll talk about dice pools and advantage/disadvantage concepts. We’ll also discuss the probability curve of rolling two or more dice together. I appreciate you. Have a wonderful day.

Author: Jeff Craigmile

I'm a tabletop role-playing game writer and designer from Des Moines, Iowa. I'm the father of four boys and human to three cats.

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