DM 101 – the basics

Getting into this game can be daunting even for an experienced RPG gamer like myself. I had so many basic D&D questions that I had google the answer for. Even now, I regularly have to refer back to saved posts and pages in my Evernote notebook. I have compiled this list of basic questions, my DM 101, for both my own reference and in the hope that it’ll help others.

Cover art of official D&D Players Handbook
The official D&D Players Handbook

The good news is that main book you need to answer all these questions (with the exception of two) is the Official Player’s Handbook rather than the Dungeon Master’s Guide. In the answers below, I will give the page number in the format of PHBXXX, where XXX is the page number. I am working from the 6th printing of the Player’s Handbook for 5th edition. There is an errata available from Wizards of the Coast but I found it contained very minor corrections.

For the Dungeon Master’s Guide, I’m working from the 5th edition and again the errata was very minor.

Characters

How to calculate Armor Class (AC)

Your AC depends on the armor you are wearing. See PHB145 for the AC of each different type of armor.

For Barbarians, Unamored Defense PHB48, equals 10 + DEX modifier + CON modifier.

Without armor or a shield, your character’s AC equals 10 + their DEX modifier – see PHB14.

How to calculate Hit Points (HP)

The method of calculating a player’s hit points are listed in the Class Features section for each class in the PHB.

How to calculate Passive Perception

Passive perception is 10 + WIS modifier + Proficiency, if applicable – see PHB175. For example:

If a 1st level charcter has a Wisdom of 14 and has proficiency in Perception then their Passive Perception is 10 + 2 + 2 = 14.
If a 9th level character has a Wisdom of 14 and no proficiency in Perception, then their Passive Perception is 10 + 2 + 0 = 12.
If a 9th level character has a Wisdom of 14 and has proficiency in Perception, then their Passive Perception is 10 + 2 + 4 = 16.

How to calculate Saving Throws

A saving throw is a 1d20 roll + the appropriate ability modifier + proficiency, if applicable – see PHB179.

Each class has proficiency in at least two saving throws, as listed in their Class Features section.

The appropriate ability modifier depends on the type of save, which might already be prescribed in the situation by the rules or campaign text, or at the DM’s discretion. The list of skills on the Player Character sheet, shows what type of ability modifier is applied to that type of skill. Abilities are described in PHB175-179.

How to determine how many Hit Points are recovered during a rest

You can expend hit dice during a short rest to regain hit points. The number of hit dice and type available are listed in the Class Features of each class in the PHB.

A player can choose to roll any number of available hit dice and add the result, plus their CON modifier, to their current hit points. They do not need to nominate the number up front but can roll each one in turn – see PHB186.

Players regain hit dice up to half their level after a long rest – see PHB186.

How to determine Modifiers

Modifiers are the + and – numbers associated with Strength, Dexterity, Consitution, Intelligence, Wisdom and Charisma. They are derived from the total numbers for these ability scores. For example, a score of 16 means the modifier is +3, and a score of 8 means the modifier is a -1.

The table showing this relationship is on PHB13.

How to determine Proficiency Score

Your proficiency score is related to your level, and are listed in the Class Features table for each class in the PHB.
If you are multiclassing, see PHB163.

How to determine Trained Skills

Players get to choose from a list of Skills to train in Proficiencies subsection of their Class Features. Also their Backgrounds may give them additional Skills to choose from.

How to setup a Character Sheet

Coming soon.
For sub-races of Elf, such as Wood Elves, their abilities include the base abilities of Elves.

Combat

How to calculate a Critical Hit

When you roll a natural d20, you roll all the damage dice twice and then add on the modifiers – see PHB196.

How to calculate Attack Bonus for weapons

This is the bonus added onto your attack roll to see if you hit a monster, not to the damage dealt (see How to Calculate Damage done by a weapon below).

It is 1d20 + ability modifier (being STR for melee weapons, DEX for ranged ones) + proficiency bonus (if proficient).
If the total equals or exceeds the Armor Class (AC) of the monster (listed in its stats block), the attack hits – see PHB194.

How to calculate Initiative

Initiative is the order which players and monsters take turns in combat.

This is your DEX modifier. When you roll Initiative you are making a DEX check, by adding or subtracting your DEX modifier to a 1d20 roll – see PHB177, PHB189.

How to calculate Cover

Cover can increase the difficulty for a target (player or monster) to be hit – see PHB196.
– A target with half cover has +2 bonus to AC and DEX saving throws.
– A target with three-quarters cover has +5 bonus to AC and DEX saving throws.
– A target with full cover cannot be targetted.

How to calculate the damage done by a weapon

This is the dice type the weapon describes + ability modifier (STR for melee, DEX for ranged). Weapons and their damage type are listed on PHB149.

If a player is dual wielding weapons, the ability modifier only gets added to the main hand unless it is negative – see Two Weapon Fighting on PHB195.

Some class skills, e.g. a Paladin’s Dueling, may add additional bonuses to the damage roll.

The proficiency bonus is only added to the Attack Roll to see if the attack hits, not the damage roll.

How to calculate whether a creature or monster’s weapon hits a player

The DM rolls a d20 + any attack bonus from the monster’s stats block. The attack bonus is usually listed in the Actions as +x to hit.

If this figure is equal or greater than the player’s AC (see How to Calculate AC above), then the attack hits.

How to calculate how much damage a creature or monster’s weapon does to a player

The damage is usually listed in the Actions part of the monster’s stats block as Hit: X (dice) type of damage. X is the average of the dice roll in brackets, so you can take the average or roll the dice. The type of damage is listed in case the target has resistance or vunerability to that type.

How to calculate whether a creature or monster’s spell hits a player

In the monster’s stack block it lists both the Attack Bonus (for spells where the DM rolls to hit) and the Spell Save DC (for where the player rolls to resist). See the Spell section below.

What is an Attack of Opportunity?

You can make an attack of opportunity when a creature moves out of your reach. This is a melee attack using your reaction and it occurs right before the creature moves out of your reach – see PHB195.

Spells

How to calculate Attack Bonus for spells

Some spells require the caster to make an attack roll. This is the bonus added onto your 1d20 attack roll to see if you hit a monster, not to the damage dealt (see How to Calculate Spell Damage below).

The attack bonus is your spellcasting modifier + your proficiency bonus – see PHB205.

If the total equals or exceeds the Armor Class (AC) of the monster (listed in its stats block), the attack hits – see PHB194.

Your spellcasting modifier (see How to Determine Modifiers above) depends on your class:
– Bards, Paladins, Sorcerers and Warlocks use Charisma.
– Clerics, Druids and Rangers use Wisdom.
– Wizards use Intelligence.

Your proficiency bonus (see How to Determine Proficiency Score above) depends on your level.

Some spells require a saving throw to be made by the monster instead (see How to calculate Spell Save DC below).

How to calculate how many Spell Slots a character has

The number of spell slots available to each character is listed in the class table for each class in the PHB. More information about spell slots is on PHB201.

If you are multiclassing in two spellcasting classes, the spell slots available are listed on a table on PHB165.

How to calculate Spell Damage

Some spells require the caster to make a roll to see if the spell hits (see How to calculate Attack Bonus for Spells above) – see PHB205.

Others require the monster to make a saving throw (see How to calculate Spell Save DC below). – see PHB205.

The damage a spell causes is listed in its description, which start on PHB211.

How to calculate Spell Save Difficulty Class (DC)

Some spells require the target to make a saving throw. The DC is equal to 8 + your spellcasting ability modifier + your proficiency bonus + any special modifiers – see PHB205.

The target rolls a d20 and if the number is equal or higher to the DC, the target is not hit.

Your spellcasting modifier (see How to Determine Modifiers above) depends on your class:
– Bards, Paladins, Sorcerers and Warlocks use Charisma.
– Clerics, Druids and Rangers use Wisdom.
– Wizards use Intelligence.

Your proficiency bonus (see How to Determine Proficiency Score above) depends on your level.

If you had to use a Spell Slot, even if the spell didn’t hit, you have used the spell slots.

How to determine how many Spells a player knows

For Bards, the number of spells known is listed in the class table – see PHB53.
For Clerics, they know all spells that are of the level they have access to – see PHB58.
For Druids, they know all the spells that are of the level they have access to – see PHB66.
For Paladins, they know all the spells that are of the level they have access to – see PH84.
For Rangers, the number of spells known is listed in the class table – see PHB90.
For Sorcerers, the number of spells known is listed in the class table – see PHB100.
For Warlocks, the number of spells known is listed in the class table – see PHB106.
For Wizards, they start with 6 spells from the Wizard spell list excluding their cantrips – see PHB114.

How to determine how many Spells a player can have prepared

Bards do not prepare spells.

Clerics prepare the number of spells equal to their WIS modifer + cleric level. In addition, spells that they gain from their domain are always prepared and don’t count against the number of spells they can prepare each day – see PHB58.

Druids prepare the number of spells equal to their WIS modifier + druid level – see PHB66.

Paladins prepare the number of spells equal to their CHA modifer + paladin level. In addition, spells that they gain from their Sacred Oath are always prepared and don’t count against the number of spells they can prepare each day – see PHB84 and PHB85.

Rangers do not prepare spells.

Sorcerers do not prepare spells.

Warlocks do not prepare spells.

Wizards prepare the number of spells equal to their INT modifier + wizard level – see PHB114.

How to swap Spells

For Bards, they can replace spells when they level – see Spells Known on PBH53.

For Clerics, they can change the spells they have prepared after a long rest, for at least 1 minute per spell level for each spell on the list – see PHB58.

For Druids, they can change the spells they have prepared after a long rest, for at least 1 minute per spell level for each spell on the list – see PHB66.

For Paladins, they can change the spells they have prepared after a long rest, for at least 1 minute per spell level for each spell on the list – see PHB84.

For Rangers, they can replace spells when they level – see Spells Known on PBH92.

For Sorcerers, they can replace spells when they level – see Spells Known on PBH101.

For Warlocks, they can replace spells when they level – see Spells Known on PBH107.

For Wizards, they can change the spells they have prepared after a long rest, for at least 1 minute per spell level for each spell on the list – see PHB114. Each time a wizard levels they can add two new spells to their spellbook for free. If they find other spells on their adventures they can copy this into their spellbooks but it costs time and gold – see PBH114.

Dungeon Mastering – the basics

Armor Chart

For a list of Light, Medium and Heavy Armor – including Shields – see PHB145.

Equipment Items

For a list of Adventuring Gear that players might find or purchase – see PHB151.

How to scale encounters

To scale the difficulty of an encounter, or scale up or down for the numbers of players – see DMG82-83.

Magic Items

For the Magic Item tabels, see DMG Chapter 7 from DMG135 onwards.

Skill Descriptions

For examples of what type of Skill a player might be trying to utilise – see PHB175-179.

Spell Descriptions

Spell Descriptions and Lists are in Chapter 11 – see PHB207.

Weapon Table

For a list of Simple and Martial melee and ranged weapons – see PHB149.

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D&D Dungeon Master - the basic DM 101
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D&D Dungeon Master - the basic DM 101
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DM 101 - the basics
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The New Dungeon Master
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