Thinking About Dice Systems
Some public domain dice

When I’m coming up with a game, it’s easiest if I start with a dice mechanic that I already understand. It’s a big advantage – there is less to playtest, fewer decisions need to be made, and I can get right to designing the fun parts of the game. This is why I love hacking games so much – the dice system is already there, I just need to improve how its used. I thought I would share some of my reflections on various dice systems. Maybe it’ll save you some time in designing your own game. Some familiarity with the games listed will help – I’m not going to explain them all in any detail.

And, of course, you can always design your own new genius dice system. But in case unique dice aren’t important to you…

Fate Dice

I love Fate. Fate dice are great because the scale of success is the same as the scale of ability. That is, you know +3 means your character is Good at something, and you know that +3 is a Good result. This is very simple and direct, compared to a target number system like D&D for example. Is a +3 good in 5E? Not sure. Kind of? Not if you’re trying to roll against a DC of 20. I watch DMs struggle to interpret middling results, partly for this reason. The player rolls an 11 to do something. It feels too high for a failure, but definitely isn’t a great result. Fate dice simplify and clarify this problem completely. I have a pile of hacks for Fate Core for a reason.

Kids On Bikes Dice

Kids On Bikes uses a single die against a moving target number. Your die might be a d4 up to a d20. This is simple, and the die clearly shows how good you are at what you are doing, but also introduces some problems. For one, with a target number of 5+, a character with a d4 cannot succeed. With moving target numbers, it is hard to hold in your mind how likely you are to succeed. The probability isn’t intuitive. So you get a very simple system, one die at a time, but you need to think through how a moving target number affects those rolls.

Call of Cthulhu Dice

Call of Cthulhu is a venerable and popular system. One reason, I think, is that it uses a percentile system. A huge benefit to a percentile system is that the chance of success is always obvious. If you have a 50% chance or a 75% chance, there you go. Over time CoC has added degrees of success, which is a big benefit for a percentile system that is usual just a binary succeed/fail result. These degrees of success require a little bit of math, figuring out what half and one fifth of 73 is, but I think it’s worthwhile in-game. You could also just eyeball it – if you make the roll by a wider margin, you get more of a result, and the opposite for failing by a larger margin. A percentile system is also great for incremental improvement. Going from a +3 to +4 is a 33% increase, but you can increase percentile skills bit by bit and still feel like you’re making progress while not unbalancing the system.

Blades in the Dark Dice

I have yet to play Blades in the Dark, but having read through the book it seems that the dice system is designed to function in the 1-4 d6s range. I like the dice system, but it doesn’t have much room for variety – similar to PbtA’s -2 to +3 range. In terms of probability, though, there is more difference between 2 and 3 BitD dice than between +2 and +3 in PbtA, I think. Anyway, BitD is a good option if you don’t want much granularity. If you have a bad/good/better/best type system for ranking abilities, this dice system would work well.

Genesys Dice

I love the idea behind Genesys dice (or Edge of the Empire dice). In practice, interpreting a dice roll slows down game play drastically, and the system ends up presenting information you don’t necessarily need or that is hard to interpret in the moment. On the other hand, the system provides a lot that other dice systems don’t, and I like that. I like that your roll result can be a combination of failure but advantage, or a combination of success but growing threat. In my opinion, though, the system requires an online dice roller, or the app from Fantasy Flight, or else a lot of table time is spent interpreting your dice-roll, and that’s time spent without anything happening in the fiction. That being said, you get much more from a single dice-roll in Genesys than you do from any of these other dice systems I mention.

D&D Dice

OK grandpa, here we go. D20 + bonus vs target number is what like 95% of tabletop RPG players are doing when they roll dice. But wait, there’s more! They also roll single dice, and pools of dice, for things like damage and spell effects and recovery. They roll percentile dice for random tables and 4d6 for character creation and various dice for hit points. Part of the fun of D&D is that you get to break out and use all of your dice. The downside is that everything is an exception. You can only sometimes guess how a mechanic will work – compared to, say, Fate or PbtA. Tools like DND Beyond help a lot, but the only reason that designers are trying to hack 5E for other games and genres is its ubiquity. Designing new things for D20 style games is a nightmare compared to other systems.

Old School/OSR Dice

Is that you great-grandpa? D&D’s profusion of different dice mechanics has deep roots, and the oldest editions of D&D sometimes read like different people designed each dice mechanic without talking to each other. This was exacerbated by not always referring to dice in the core texts – you’d read something like “3-17 appearing” and have to think for a moment to realize that must be 2d8+1 and not 3d6-1. Some abilities are a percentile, some are based on a d6, and some use a d20 to roll high while others use a d20 to roll low.

World of Darkness Dice

It’s known that the World of Darkness took its dice system largely from Shadowrun, but they improved it by removing exploding dice. Dice pool + exploding dice with d6s is just…it’s madness.There is a lot to like about the world of Darkness dice system. You get to roll big handfuls of dice when you are good at something – its rewarding in a tactile way. There are also two sliding scales – number of dice, and target number you want on each die. The problem there is that probability quickly gets away from you. Is it better to roll 7 dice at difficulty 7, or 8 dice at difficulty 8? In the moment, who the heck knows? Later editions of the World of Darkness addressed this by keeping a fixed target number, but I still like the sliding target number as an additional variable. You just need to be careful about what kinds of things can change the target number compared to what adds or subtracts dice.

Powered by the Apocalypse Dice

Even I have tried my hand at a few PbtA hacks – the system is very easy to design for because everything is an exception. If you want a mechanic for something, write a move. If not, then just describe what happens. The dice system is very simple and straightforward. There is no real mechanic for making something more or less difficult (without writing multiple moves for the same thing at varying difficulty) but the system is tuned to aim toward failing slightly less than 1/2 the time and most often getting a marginal success. The key here is to make sure that failure is interesting, since it will come up often, especially with a -1 or -2 ability. Games like Dungeon World do this by letting the player mark experience when they fail, which is often enough to at least dull the sting. Most PbtA games also let the GM escalate the situation on a ‘miss’ of 6 or less, a kind of “no, and” style failure that is more interesting than a simple “no.”

Savage Worlds Dice

Savage Worlds never uses all of the usual dice except the D20, and the target number is always the same – a 4. The addition of a coin-flip “wild die” d6 to every PC roll also helps make success much more likely, which fits the fast-and-fun pulp style of SW. (“coin flip” meaning you have a 50% chance of success on a d6)

Mouse Guard/Torchbearer Dice

I love both Mouse Guard and Torchbearer, but the dice for both are basically a coin toss. You roll d6s against a target number of 4 or higher and count successes. Occasionally you can actually spend a resource to re-roll the dice that come up 6s, so there’s a little bit of the fiddling around that I enjoy, but I’d rather a little more variety than a 50/50 chance on every die. That being said, it’s simple, easy to remember, uses dice you already have, and I’ve had fun playing both games.

Parsec Dice

I know, probably none of you have heard of Parsec. It’s the game I published in 2012 through Jolly Roger Games. It uses d6s where the number of dice rolled are based on your attribute plus/minus modifiers and the target number for those dice is based on your skill. The advantage is that what you roll is set and clear without having to ask the GM each time. If you roll 5 dice with a target number of 3 or higher, then you can shorthand that as 5@3. Not world-shattering, but I’m still proud of the game, especially as my first published game.


When choosing a dice system, considerations include:

  • How long does it take to interpret what the dice say?
  • How often is success likely, and does that fit with your genre and expectations for play?
  • Is it clear to the player how likely success is with a given roll?
  • What is the tactile feeling of rolling? Are you rolling too many dice? Too few? Like ‘mouth feel’ for wine, what is the intended ‘table feel’ for your dice system? Everything hinges on a single die? Or heaps of dice skittering everywhere, to be collected and counted up?
  • Do you need special or unusual dice, or can you just grab what’s in a board game box and play?
  • Is there a way to get the same information with fewer, or simpler, dice?
  • What does the handful of dice mean? Is it the character’s total ability (World of Darkness)? Is part of it the difficulty they face (Genesys)? Is it all of the advantages they have (D&D advantage, bless, bardic inspiration)?
  • Are the dice clear without asking the GM? For example,
  • have to ask for a DC for your d20 roll, but rolling damage dice is obvious as you’re just adding them up.

What are your favorite dice? What is your favorite dice system?