In order to simplify and make clearer the different ways in which dice can be rolled and modified, game designers have developed a system of dice notation. These semi-formula looking notations indicate how many dice of whihc type to roll, and how to modify the results.

The most common form of notation is simply the use of Dn to indicate the type of dice being used, where n is the number of sides the die has. Thus a normal six-sided die is noted as a D6, while a die with 20 sides becomes a D20. A number prior to the D indicates how many of that type of dice should be rolled. Thus 3D6 means to roll three six sided dice. 2D12 means to use two dice each of twelve sides, and so on. When using this notation, it is generally (but not always) assumed that the dice should be added together to generate a single sum.

It is also common to indicate modifiers to the dice rolls. These are numbers that should be added to the sum of the dice rolled. Thus 2D10+3 means to roll two D10 and add three to the sum. This creates a range of outcomes from 5 – 23. Of course, modifiers may ask you to subtract or multiply the dice. These notations can even be strung together like a mathematical formula. For example, 2D8+2D4 means to roll two eight-sided dice and two four-sided dice and add the dice together.

The use of parenthesis can indicate how to roll and modify the dice. For example 2D6+(D10+1) would mean to roll a ten-sided die, add one to it, and then add that result to the sum of two six-sided dice.

There are more esoteric possibilities but these are rarely used in most gaming situations. The simple 2D6 or 3D4+2 notations will cover most die rolls a gamer is likely to come across.