Multiclassing allows you to gain levels in multiple classes. Doing so lets you mix the abilities of those classes to realize a character concept that might not be reflected in one of the standard class options.
With this rule, you have the option of gaining a level in a new class whenever you advance in level, instead of gaining a level in your current class. Your levels in all your classes are added together to determine your character level. For example, if you have three levels in wizard and two in fighter, you’re a 5th-level character.
As you advance in levels, you might primarily remain a member of your original class with just a few levels in another class, or you might change course entirely, never looking back at the class you left behind. You might even start progressing in a third or fourth class. Compared to a single-class character of the same level, you’ll sacrifice some focus in exchange for versatility. – Players Handbook
The basic idea behind Multiclassing in D&D is that you can add any other class to your original choice as you level up. Whatever class you choose starts from level 1.
So as a basic example you can start as a level 1 Fighter. When you have enough experience to get to level 2, you could pick Cleric. At that point you’d be a multiclassed level 1 Fighter and level 1 Cleric.
We put together a list of what we consider the Best Multiclass Combos. There are also guides by Class, including:
Understand that these concepts tend to stay the same, but the exact mechanics can change. For example, in D&D 5th edition there are (as of this writing) ability score prerequisites for multiclassing. Here they are:
|Class||Ability Score Minimum|
|Fighter||Strength 13 or Dexterity 13|
|Monk||Dexterity 13 and Wisdom 13|
|Paladin||Strength 13 and Charisma 13|
|Ranger||Dexterity 13 and Wisdom 13|
As of now that is in the Players Handbook. Your game is your own and D&D gives you the opportunity to do what you want. If your DM and group wanted to ignore these you are of course free to.
If anyone out there is playing Baldur’s Gate 3, which is officially based on D&D 5e rules, you’ll see there are no prerequisites to multiclassing. You can pick any class at any time with any stat distribution.
In general, Wizards of the Coast is trending towards maximizing choices. That means reducing restrictions.
Next lets look at how this all works with Experience, Hit Points, Features and Spells:
The experience point cost to gain a level is always based on your total character level, as shown in the Character Advancement table, not your level in a particular class. So, if you are a cleric 6/fighter 1, you must gain enough XP to reach 8th level before you can take your second level as a fighter or your seventh level as a cleric. – Players Handbook
Pretty simple, you still progress as a total, not based on each class.
It’s this feature that makes multiclassing balanced. Too much and you really can dilute your character.
Hit Points and Hit Dice
You gain the hit points from your new class as described for levels after 1st. You gain the 1st-level hit points for a class only when you are a 1st-level character.
You add together the Hit Dice granted by all your classes to form your pool of Hit Dice. If the Hit Dice are the same die type, you can simply pool them together. For example, both the fighter and the paladin have a d10, so if you are a paladin 5/fighter 5, you have ten d10 Hit Dice. If your classes give you Hit Dice of different types, keep track of them separately. If you are a paladin 5/cleric 5, for example, you have five d10 Hit Dice and five d8 Hit Dice. – Players Handbook
Hit Dice come into play mostly on rests. You can typically heal for one or more Hit Dice on a short rest. So you’d keep track of which you spend for each class.
Your proficiency bonus is always based on your total character level, not your level in a particular class. For example, if you are a fighter 3/rogue 2, you have the proficiency bonus of a 5th-level character, which is +3. – Players Handbook
So Proficiency bonus is based on total character level, pretty straight forward.
When you gain a new level in a class, you get its features for that level. You don’t, however, receive the class’s starting equipment, and a few features have additional rules when you’re multiclassing: Channel Divinity, Extra Attack, Unarmored Defense, and Spellcasting. – Players Handbook
Class features are one of the biggest reasons to multiclass. Things like Fighting Styles, Action Surge, Spellcasting, Channel Divinity… are enormously powerful additions to a character that didn’t have them previously.
The thing to understand is they typically don’t stack. So getting “Extra Attack” twice is not going to give you anything, for example.
If you already have the Channel Divinity feature and gain a level in a class that also grants the feature, you gain the Channel Divinity effects granted by that class, but getting the feature again doesn’t give you an additional use of it. You gain additional uses only when you reach a class level that explicitly grants them to you. For example, if you are a cleric 6/paladin 4, you can use Channel Divinity twice between rests because you are high enough level in the cleric class to have more uses. Whenever you use the feature, you can choose any of the Channel Divinity effects available to you from your two classes. – Players Handbook
Normally you get one Channel Divinity until you get to a high enough level. Getting another class with it wont stack, essentially.
If you gain the Extra Attack class feature from more than one class, the features don’t add together. You can’t make more than two attacks with this feature unless it says you do (as the fighter’s version of Extra Attack does). Similarly, the warlock’s eldritch invocation Thirsting Blade doesn’t give you additional attacks if you also have Extra Attack. – Players Handbook
This is the example I gave above. Extra Attack is very powerful, and will not stack if you multiclass.
If you already have the Unarmored Defense feature, you can’t gain it again from another class. – Players Handbook
Same as the others, no stacking.
The basic idea is if you have 2 classes that can cast spells, track them individually for purposes of what you know and can prepare.
For example a Druid / Wizard multiclass character tracks his or her Druid and Wizard classes individually for known and prepared spells.
For Spell Slots, you add the spell slots from all classes that can cast, and then consult the table below – Multiclass Spellcaster: Spell Slots per Spell Level
Here are the Players Handbook Rules on it specifically:
Your capacity for spellcasting depends partly on your combined levels in all your spellcasting classes and partly on your individual levels in those classes. Once you have the Spellcasting feature from more than one class, use the rules below. If you multiclass but have the Spellcasting feature from only one class, you follow the rules as described in that class.
Spells Known and Prepared. You determine what spells you know and can prepare for each class individually, as if you were a single-classed member of that class. If you are a ranger 4/wizard 3, for example, you know three 1st-level ranger spells based on your levels in the ranger class. As 3rd-level wizard, you know three wizard cantrips, and your spellbook contains ten wizard spells, two of which (the two you gained when you reached 3rd level as a wizard) can be 2nd-level spells. If your Intelligence is 16, you can prepare six wizard spells from your spellbook.
Each spell you know and prepare is associated with one of your classes, and you use the spellcasting ability of that class when you cast the spell. Similarly, a spellcasting focus, such as a holy symbol, can be used only for the spells from the class associated with that focus.
Spell Slots. You determine your available spell slots by adding together all your levels in the bard, cleric, druid, sorcerer, and wizard classes, and half your levels (rounded down) in the paladin and ranger classes. Use this total to determine your spell slots by consulting the Multiclass Spellcaster table.
If you have more than one spellcasting class, this table might give you spell slots of a level that is higher than the spells you know or can prepare. You can use those slots, but only to cast your lower-level spells. If a lower-level spell that you cast, like burning hands, has an enhanced effect when cast using a higher-level slot, you can use the enhanced effect, even though you don’t have any spells of that higher level.
For example, if you are the aforementioned ranger 4/wizard 3, you count as a 5th-level character when determining your spell slots: you have four 1st-level slots, three 2nd-level slots, and two 3rd-level slots. However, you don’t know any 3rd-level spells, nor do you know any 2nd-level ranger spells. You can use the spell slots of those levels to cast the spells you do know — and potentially enhance their effects.
Pact Magic. If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.
Multiclass Spellcaster: Spell Slots per Spell Level