Dungeons and Dragons 5e – Footnotes on Mechanics

In this post, I make an attempt to explain mechanics and rules in Dungeons and Dragons 5th Edition that I found confusing when I first started playing.


Ability Score Modifier – The number with a + located above or below an ability score or stat. A character with a DEX Ability Score of 16 has a +3 DEX Modifier.

Under normal circumstances, Player Characters (PCs) can only reach a maximum of 20 for any given Ability.

Proficiency Score – Determined by character level. Can be added to rolls for weapons, skills and abilities. Usually starts at +2 for 1st level characters. This represents what actions or skills the character will be able to perform easier due to mastery or practice.

Initiative – When the character will be able to act in a round relative to all other combatants. Dictates when your turn will be.

  • Initiative Bonus = DEX Modifier. If you have +2 to DEX, you have +2 Initiative bonus when rolling for Combat Initiative.

Perception – How adept the character is at taking their surroundings in. Basically the numerical equivalent of how well one can notice anything unusual or noteworthy while doing something else (traveling, taking a break, etc.).

  • Passive Perception = 10 + WIS Modifier + Proficiency (only if proficient)

Hit Dice – The type of dice the character uses to regain HP on short rests and when adding to their max HP upon leveling up. The number of hit dice that a character can use for short rests is determined by their level (2nd level Barbarian can use 2d12). When this number is exhausted, the character must finish a long rest to regain all hit dice consumed.

Advantage/Disadvantage – Makes the player roll twice the number of d20 dice and select the higher (Advantage) or lower (Disadvantage) and use that number for that specific attack roll, save, or ability check.

NOTE ON LEVELING UP: Whenever a character gains a level, make sure to have all skills reflect any changes in proficiency bonus and/or Ability Scores (if any). A 4th level Wizard that used to have 17 INT (+3) but increased that value to 19 INT (+4) now operates more effectively when using skills and actions relating to that stat. Upon reaching 5th level, their Proficiency Bonus is also increased to +3.

3rd Level Wizard (+3 INT, +2 Prof):

  • Spell Attack Roll = 1d20 + 3 + 2
  • Investigation (Proficient) = 5 (+3 INT + 2 Prof)
  • Spell Save DC = 13 (8 + 2 Prof + 3 INT)

4th Level Wizard (+4 INT, +2 Prof):

  • Spell Attack Roll = 1d20 + 4 + 2
  • Investigation (Proficient) = 6 (+4 INT + 2 Prof)
  • Spell Save DC = 14 (8 + 2 Prof + 4 INT)

5th Level Wizard (+4 INT, +3 Prof):

  • Spell Attack Roll = 1d20 + 4 + 3
  • Investigation (Proficient) = 7 (+4 INT + 3 Prof)
  • Spell Save DC = 15 (8 + 3 Prof + 4 INT)

CON Modifier increases also affect maximum HP gain. If a character gains a +4 CON modifier from their previous +3, they add an additional 1 Max HP for every previous level they gained prior to the increased modifier.

Money Conversion
Let’s be honest. Most players will only care about Gold (GP) and Silver (SP). But on the off chance that you encounter other currencies, here’s how much is needed to convert to and from GP:

100 Copper = 1GP
10 Silver = 1GP
2 Electrum = 1GP
1 Platinum = 10GP

For all other Dungeons and Dragons 5e currency conversions, refer to this table:



Extra Attack – Allows characters with this feature to attack twice (or more, in the case of high level Fighters) when they take the Attack action. For dual weapon characters, this translates to make multiple attacks with the main hand weapon and always only one for the offhand weapon. This is due to the offhand swing being defined as a bonus action. To make things simple, always think of the offhand swing as the final flourish. Note the distinction between Attack and attack as used in the rules.


  • A 20th level Fighter that uses Two Weapon Fighting and activates their Action Surge while buffed with the Haste spell can make a total of 10 attacks. 9 of those are from the main weapon, while the last one is from the offhand.

Attack Action (4 main) + Action Surge Attack (4 main) + Haste bonus (1 main) + Bonus action (1 offhand) = 10 attacks total.

    • Extra Attack at 20th level grants a total of 4 attacks when taking the Attack action.
    • Action Surge grants the ability to make another Attack action, triggering another possible 4 attacks.
    • Haste grants the last main weapon attack. This is due to the limitation on the spell which reads …action can be used only to take the Attack (one weapon attack only)
    • The last attack (10th) comes from the bonus action that can be used to swing with the offhand weapon.

Rolling to Attack =/= Rolling for Damage. With this roll, you’re still trying to determine if the attack you want to make will hit the enemy. Unless otherwise specified by special spell/class/race features, this is how an attack action usually plays out during combat:

Attack Roll = 1d20 + Ability Score Modifier + Proficiency
If the resulting number is greater than the target’s Armor Class or AC, the attack is a hit.

Damage Roll = (Dice specified by weapon type/description) + Ability Score Modifier


  • A 1st level Barbarian (without Rage status) decides that it wants to smack a Giant Rat with its Greataxe – a weapon that uses 1d12 to determine damage.
  • The Barbarian’s current STR is 16, which grants that stat a +3 Ability Score Modifier.
  • At 1st level the Proficiency bonus added will be +2.
  • The Giant Rat’s AC is 12. If the Attack Roll is 12 or greater, the Barbarian lands a blow. If the value is 11 or lower, the attack misses.
  • The resulting damage (on a hit) would be then calculated as 1d12+3.

Weapon Attack Roll = 1d20 + 3 + 2
Damage Roll = 1d12 + 3

Let’s just assume that the player rolls 7 on the Attack Roll. With the addition of the modifier and proficiency, the total becomes 12. This allows the Barbarian to successfully hit the Giant Rat. For the damage roll, lets say that the d12 result was a disappointing 4. Fortunately adding the Ability Score Modifier makes it a total of 7, which is still a respectable amount of damage.

Spell damage usually does not add the Spellcasting ability modifier to the damage dealt, but there are some exceptions to this like Agonizing Blast. This Eldritch Incantation allows Warlocks to add their Charisma ASM to the damage dealt by their Eldritch Blast.

Spell Damage Roll = (Dice specified in the spell description)

Turn = One character or environmental feature decides what it does for the round
Round = All combatants each take their turns
Turn Order = The sequence in which combatants perform their desired actions (spellcasting, swinging a weapon, moving, doing nothing, etc.)

One round of combat happens in 6 seconds. Which means that spells that have a duration of one minute will stay in effect for 10 rounds of combat (60 Seconds). A round ends when all participants involved have taken their turn.

Other mechanics and rules will be added in the future. Because I still get confused most of the time.

– D

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