SpiralWorlds Player’s Manual · Before Character Creation

Dice & Core Rolls

Dice notation · d20 tests · advantage · natural rolls · edition differences

You can use physical dice, a digital dice roller or both. What matters is knowing which die to roll, which modifiers apply and what number you are trying to meet. The three supported rules systems all use a d20 heavily, but they do not treat every natural 20, natural 1, multiplier or special roll in exactly the same way.

Typical polyhedral roleplaying dice including d4 d6 d8 d10 d12 and d20
A standard RPG set normally contains d4, d6, d8, d10, d12 and d20 dice, with two d10s often used together for percentile rolls.
Most important novice rule: a natural 20 is not a universal automatic success on every kind of roll. Read the rule for the kind of roll you are making and for the edition you are playing.

Read dice notation

What 3d4 + 3 means

First numberHow many dice to roll. In 3d4, roll three dice.
The dMeans “die” or “dice.” It separates quantity from die size.
Second numberThe number of sides. In 3d4, each die has four sides.
ModifierAdd or subtract the number after the dice. 3d4 + 3 means total the three d4s, then add 3.

Common dice: d4, d6, d8, d10, d12 and d20. A notation such as 2d6 means roll two six-sided dice and add them together.

Percentile / d100: roll two d10s, using one for tens and one for ones. A result of 70 and 1 is 71; 00 and 0 represents 100.

The basic d20 pattern

Roll high, add the right modifiers, compare to a target

  1. Roll a d20.
  2. Add the modifiers required by the rule.
  3. Compare the total with the target number. If the total equals or exceeds the target, the roll normally succeeds.

The details of the modifier and target depend on the roll: an attack usually compares with Armor Class, a skill or ability check with a Difficulty Class, and a saving throw with a save DC.

Edition rules

Use the right d20 procedure

D&D 5.5e / 2024

The current rules call the game’s three main d20 rolls D20 Tests: ability checks, saving throws and attack rolls.

1. Roll 1d20. If the roll has Advantage or Disadvantage, roll two d20s instead and use only one result.

2. Add modifiers. Add the relevant ability modifier, Proficiency Bonus if relevant, and any circumstantial bonuses or penalties.

3. Compare with the target. Ability checks and saves normally compare with a Difficulty Class (DC); attack rolls compare with Armor Class (AC).

Advantage: roll two d20s and use the higher. Disadvantage: use the lower. Multiple instances do not stack, and one Advantage plus one Disadvantage cancel each other.

Natural 20 / natural 1: under the general 2024 D20 Test rules, a natural 20 automatically hits on an attack roll and is a Critical Hit; a natural 1 automatically misses an attack. Do not automatically apply that attack-roll rule to every ability check or saving throw unless a specific rule says to do so.

Rounding: follow the rule that creates the fraction. Current rules often state whether to round down or up for that calculation; do not import the older 3.x multiplier-combination rule unless a 2024 rule actually instructs you to use it.

Pathfinder 1e

PF1e usually follows the classic d20 pattern: roll d20, add the relevant attack, save, skill or other modifier, and compare with AC, DC or another target.

Attacks: natural 1 always misses and natural 20 always hits. A natural 20 can also threaten a critical hit, which normally requires a confirmation roll under PF1e critical-hit rules.

Saving throws: natural 1 is an automatic failure and natural 20 is an automatic success.

Skill checks: do not treat natural 20 as an automatic success or natural 1 as an automatic failure unless a specific rule says otherwise.

No core Advantage mechanic: PF1e uses its own bonuses, penalties, rerolls and special rules rather than the 5.5e Advantage/Disadvantage system.

Fractions and multipliers: PF1e’s inherited 3.x-style rules generally round fractions down unless a rule provides an exception. When multiple multipliers apply to an abstract value, do not simply multiply them together; for example, ×2 combined with ×2 normally becomes ×3. Real-world measurements such as weight use ordinary multiplication.

D&D 3.5e

3.5e also uses d20 + modifiers against a target for attacks, saves and skills, but its natural-roll rules are specific to the type of roll.

Attacks: natural 1 always misses and natural 20 always hits. A natural 20 is also normally a critical threat requiring confirmation.

Saving throws: natural 1 automatically fails and natural 20 automatically succeeds.

Skill checks: natural 20 is not automatically a success and natural 1 is not automatically a failure.

No core Advantage mechanic: use the bonuses, penalties and rerolls supplied by 3.5e rules.

Fractions: generally round down unless a rule gives an exception. Multipliers: for abstract values, multiple multipliers combine additively after the first: ×2 and ×2 normally become ×3. Real-world measurements use ordinary multiplication.

Edition trap: the PF1e and 3.5e multiplier language is very similar. That does not mean their skill modifiers, class bonuses, combat manoeuvres or other rules are interchangeable.

Before play

Know the rolls on your own sheet

You do not need to memorise the whole rules system. For your first session, know how to find and roll these:

  • Your most-used weapon attack.
  • Your weapon’s damage dice.
  • Your Initiative modifier.
  • Your important skill/check modifiers.
  • Your saving throws.
  • Your Armor Class.
  • Your maximum and current Hit Points.
  • If you cast spells, your spell attack modifier and spell save DC.
  • Any feature that grants Advantage, a reroll, a bonus die or another special roll.
Say the result, not just the die. If you roll 13 and your modifier is +5, tell the Games Master “18,” unless they specifically ask for the natural die result.

Ready to create a character

Dice checklist

  • You can identify d4, d6, d8, d10, d12 and d20.
  • You understand notation such as 2d6 + 3.
  • You know how percentile dice work.
  • You know which edition the campaign uses.
  • You have not assumed that natural 20 means automatic success on every roll.
  • 5.5e Advantage/Disadvantage has not been imported into PF1e or 3.5e by default.
  • PF1e/3.5e multiplier rules have not been imported into 5.5e.
Character CreationCharacter Sheet Reference

Sources and licensing

Rules sources

SRD 5.2.1 attribution: This work includes material from the System Reference Document 5.2.1 by Wizards of the Coast LLC, licensed under Creative Commons Attribution 4.0 International.

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