In a modifier system like Dungeons & Dragons you roll one die, add a bonus and compare the total to a target. A dice-pool system works differently: you gather a number of dice determined by your character’s skill, roll them all at once, and count how many land on a “good” face. The size of the pool is the character. This is the engine behind Shadowrun, the World of Darkness games, the newer editions of Warhammer’s roleplaying lines and dozens of indie titles.
Hits, thresholds and target numbers
Two ideas do most of the work in any pool system.
- The target number is the face a single die must show to count. Roll each die; anything at or above the target is a hit (also called a success).
- The threshold is how many hits the whole roll needs to succeed at the task. An easy action might need one hit; forcing a reinforced door might need four.
So a roll resolves in two steps: count the hits in your pool, then compare that count to the threshold. You are not chasing one high number — you are trying to accumulate enough good dice.
Three families of pool
The details vary by game, but most pools fall into one of these shapes.
| System | Dice & what counts as a hit |
|---|---|
| Shadowrun | A pool of d6; each die showing 5 or 6 is a hit. Your pool is skill + attribute, and the more dice you throw the more hits you tend to net. |
| World of Darkness / Storyteller | A pool of d10; each die at or above a target (commonly 8) is a hit. Many editions let a 10 count double or trigger a re-roll. |
| Warhammer (dice-pool editions) & wargames | Buckets of d6 rolled together — roll to hit, roll to wound, then a save — counting successes at each step rather than summing. |
Because you are counting rather than adding, resolving a huge pool is fast: sweep the failures aside and tally what is left.
Botches and glitches
Many pool games track the bad face as well as the good one. In classic World of Darkness a die showing 1 could cancel a hit, and a roll with no hits but one or more 1s was a botch — not just failure but something going actively wrong. Shadowrun uses a related idea called a glitch: if more than half your dice come up 1, the action misfires even if you also scored hits, and a glitch with zero hits is a critical one. These rules give a pool a dramatic downside that a flat modifier roll lacks: a big handful can still turn sour.
Why bigger pools mean reliability, not just power
This is the part players often get backwards. Adding dice to a pool does raise your average number of hits — but its more important effect is to tighten the spread. With a Shadowrun-style d6 pool, each die is a hit about a third of the time, so the expected hits are roughly one for every three dice. A pool of three dice might swing wildly between zero and three hits from roll to roll. A pool of twelve will cluster reliably around four hits, and almost never produces nothing at all.
In statistics this is the difference between the mean and the variance. A single d20 is extremely swingy — every result from 1 to 20 is equally likely. A large pool behaves more like a smooth bell: the extreme outcomes get rarer as the pool grows, so a highly skilled character doesn’t just hit higher numbers, they fail far less often. That consistency is exactly what “being good at something” should feel like, which is a big part of why designers reach for pools.
Reading the odds at the table
A useful habit is to think in expected hits. Estimate the fraction of dice that count — a third for 5-or-6 on d6, three in ten for 8+ on d10 — and multiply by your pool. If the threshold sits comfortably below that expectation, the action is a near-certainty; if it sits above, you are gambling on a lucky spread. Trying the same pool a few times makes the clustering obvious in a way that a table of numbers never quite does.
Pools reward specialisation, punish over-reaching with botches, and turn probability into something you can feel in your hand. If you want to see the clustering for yourself, roll a few different pool sizes and watch how the count of successes settles down — you can throw a whole handful at once and read the result instantly.
Try it yourself. Dice Drop rolls real physics dice in your browser — pools, exploding dice and modifiers built in.
🎲 Roll dice freeKeep reading: exploding dice explained, or how roll-under and roll-over systems compare.