Never Tell Me The Odds (Of My Defective Dice)


Note: For those of you keeping track this is our second featured article by guest writer J, revisited from a series he wrote for Please enjoy.

So, as much as it pains me to do it, it looks like I owe the D20 system an apology. For years (well, decades now- eek!) I have disliked the D20 family of RPGs. Having cut my fangs on Shadowrun and GURPS the idea of classes and levels never set well with me. I never liked hitpoints. I downright hate rolling a single die at a time (regardless of the type) and the D20 rolls like a beach ball. It’s way too easy to lose the result because of an accidental nudge- which forces another roll, which inevitably travels the full length of the table, over the edge and into some dark corner room. But more than anything, D20s just never roll well for me.

Now, understand that I am a notoriously bad roller even on my best days, but the D20 is my bane. I’ve had entire sessions where I never rolled above a 10. And when you’re playing with mini-maxi munchkins you’d better believe your roll needs to be 16 or greater to be effective. Add to this the general opinion at the table that my poor rolling wasn’t just bad luck but a personal failing on my part, and you can see why I’m hesitant to commit to a D20 campaign.

But it is only recently that I learned my fellow players weren’t just assholes. They were right!

Photo provided by police in Pratteln near Basel, Switzerland, shows a donkey that fell into a hole on Saturday, Nov. 1, 2014. Firefighters could rescue the animal from its predicament. (AP Photo/Keystone, Police Basel Landschaft) MANDATORY CREDIT

Pictured: One of my former players

I happened to see this YouTube video about testing your D20s using an old golfer’s trick. You take a small cup of water, saturate it with salt until the D20 floats, then you spin it several times to see what numbers come up. If the die is really off balance then you’re likely to see the same results way too often. If you get an even distribution then you’ve probably got a decently random die.

Having nothing better to do one day (that in itself speaks volumes, doesn’t it?) I set about testing my D20s just for the sake of curiosity.

At this point I should mention that I have been well aware that the polished dice from most manufacturers are less than perfect. And I have been aware of GameScience and their more accurate product. But GameScience dice were expensive and they weren’t pretty. Besides, the cheaper, prettier dice couldn’t be off that much. With all the factors of rolling included, the impact on the actual results were negligible, right?


I tested ten of my D20s. Four with the salt water cup. All four of them were Official DnD purple D20s with black numbering. I only remember buying one of them so don’t ask me where the other three came from. Maybe they reproduce while I’m not looking. Of the the four Official DnD D20s, two of them seemed OK. The other two were sadly out of balance. The first seemed to be in love with the number 13.

And we all know what sits next to 13 on a D20…

But that was OK because I rarely ever used them. With their fine black print on dark purple, in a room with subdued lighting, even a nocturnal creature like myself can’t read them more than half an arm’s length away. Besides, I never liked their color.

But my pretties? (Most of which are Chessex I believe) They sank straight to the bottom of the glass. I tried adding salt. I tried heating the water to increase the salt saturation. Nothing worked. The salt water cup wasn’t going to work for this. But now I was obsessed with learning the true odds of my dice. Half of the Official DnD D20s were significantly flawed. What quality of dice had I been entrusting my characters’ fates to?

So I took a page from the Gorn Engineering manual. If it doesn’t move, push harder! So I brute forced some percentages out of the next six. My testing method was to roll two different colored D20s together (did I mention I really hate rolling dice singularly?) and recording the results with marks on paper until all twenty sides of one of the dice had yielded five results. Ideally this would mean 100 rolls per set. In reality this meant 202, 187, and 156 rolls respectively.

I’ll spare you the excruciating details of each die (mostly because I’m too lazy to type them all in) and skip right to the most grievous results.

Of the six dice tested, half yielded more than a percentage point difference between low (1-10) and high (11-20) results. On the results of 16 or better (which should be ideally 25%) these six came in with 23.26%, 23.76%, 22.99%, 22.45% 19.23% and 30.12%. Oddly enough (get it? Oddly?) that last one with 30.12% on the 16+ results was also the only die to show a perfect 50% low / 50% high.

I learned that two of my favorite dice were consistent traitors to my cause. My lovely frost blue D20 rolled up 1.98% for 19s and my stark white D20 sported an outrageous 13.46% on 2s! In case you haven’t bothered to do the math both of those should have been at, or very near to, a flat 5%. After that I just didn’t have the spiritual strength to continue testing my other dice.

So to the whole family of D20 based RPGs, I formally apologize for trash talking your systems. I still don’t like your levels, or classes, or hitpoints, or rolling a single die at a time. But the poor rolling? That’s on me.

-- Knowyourmeme

— Knowyourmeme

Check back next week for part 3 of our guest feature by J.


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