D20 System v3.0 SRD/Basics

This material is Open Game Content, and is licensed for public use under the terms of the Open Game License v1.0a.

DICE NOTATION

These rules use the following die notations:


 * d4 = four sided die
 * d6 = six sided die
 * d8 = eight sided die
 * d10 = ten sided die
 * d12 = twelve sided die
 * d20 = twenty sided die
 * d% = percentile dice

Die rolls are expressed in the format:


 * [#] die type [+/- modifiers]

Example: 3d6+2 means: "Roll 3 six sided dice. Add the result of the three dice together. Add 2."

ROUNDING FRACTIONS

In general, if you wind up with a fraction, round down, even if the fraction is one-half or larger.

Exception: Certain rolls, such as damage and hit points, have a minimum of 1.

MULTIPLYING

Sometimes a special rule makes you multiply a number or a die roll. As long as you’re applying a single multiplier, multiply the number normally. When two or more multipliers apply, however, combine them into a single multiple, with each extra multiple adding 1 less than its value to the first multiple. Thus, a double (x2) and a double (x2) applied to the same number results in a triple (x3, because 2 + 1 = 3).

BASIC TASK RESOLUTION SYSTEM

These rules assume a standardized system for determining the success or failure of any given task. That system is:

d20 + Modifiers vs. Target Number

The Modifiers and Target Number are determined by the type of task.

If the result of the d20 roll + the Modifiers equals or exceeds the Target Number, the test is successful. Any other result is a failure.

A "natural 20" on the die roll is not an automatic success. A "natural 1" on the die roll is not an automatic failure.