In some role-playing game (RPG) systems, rather than rolling a single die to determine the success or failure of an action, the player rolls a number of dice simultaneously, known as a dice pool. The number and type of dice to be rolled are defined by the mechanics of the game.

In his 2022 paper "Icepool: Efficient Computation of Dice Pool Probabilities", Albert Julius Liu defined the term "dice pool":

While some dice mechanics determine the result from a roll of a single die, others have a player or players rolling a "pool" of multiple dice. For most such mechanics, all of the dice are thrown simultaneously and without order, with the dice being treated as indistinguishable other than the number they show. In other words, the roll of a pool is fully described by a multiset. The in-game consequences of the roll are then evaluated as a function of the multiset according to the rules of the game.

Jenny Ford of the British game publisher Man o' Kent Games points out that for a game designer, using a dice pool rather than a single die has the advantage of probability control: "Game designers want to give players a certain experience, and to give that experience they need to have some chance of predicting what will happen to their players. That means that totally random results [from rolling a single die] are difficult to use consistently to produce a desired player experience ... Rolling lots of dice at once ... will tend towards the mean." In essence, if a lot of dice are rolled, the average of all of the dice rolled will approach the mean of the die used. For example, rolling 10 six-sided dice should result in about half of the dice being 4 or more. The game designer can then express success as the number of dice with a given value — say 4 or more — allowing the designer to more accurately control the probable outcome of the desired action.

In many RPG systems, non-trivial actions often require dice rolls. Some RPGs roll a fixed number of dice, add a number to the die roll based on the character's attributes and skills, and compare the resulting number with a difficulty rating. In other systems, the character's attributes and skills determine the number of dice to be rolled.

Dice pool systems generally use a single size of die, the most common being six- or ten-sided dice (d6s or d10s), though in some games a character's Attributes or Skills may determine the size of the dice in the pool, as well as their number (such as Deadlands). While such games may require different sized dice for different rolls, the dice in a given pool are usually all the same size.

The results on each die may be added together and compared to a target number (as in Over the Edge first and second editions), or the player may count the number of dice which roll higher than a specified target number, and compare that to a required number of "successes" (as in early editions of Shadowrun or the Storyteller System). In systems using the latter method, the target number required for a success may be fixed (the same for every roll) or variable (assigned depending on the difficulty of a task); the number of successes required may indicate the degree of success, or a minimum number of successes may be required as another means of determining difficulty. Another variation is that a number of dice are rolled, but only some are added together (as in the "Roll and Keep" system used by Legend of the Five Rings and 7th Sea).

In dice pool systems it is common to add or subtract dice from the pool to represent different circumstances.