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5e: How Do Spell Slots Work?

Written by Ethan

Ethan is a storyteller, GM, and all-around nerd. He spends his time introducing all of his friends to D&D and creating hard magic systems for upcoming novels.

On the go? Listen to the audio version of the article here:

If you’ve ever wanted to play a spellcaster in D&D, you’ve encountered the term ‘spell slots’. You’re definitely not the only one who has looked at them and wondered how they work.

Spell slots are the fuel to cast spells in D&D. To cast one, you normally spend an unused spell slot of the spell’s level or higher. Ritual casting doesn’t use slots; some abilities also allow casting without spending slots. You can use available spells repeatedly or mix and match.

Is it that simple? Well, no. If you want to understand how spell slots work, how to get more of them, and how to make the most of them, keep reading.

What are Spell Slots?

A spell slot is not a physical thing. It’s not something you carry around. It is instead a measure of how much magical power you can tap in a day. Think of it as a magical power supply for spells.

When you cast a spell, it is powered by the spell slot that you are spending. When you do so, the slot is effectively ‘filled’ and cannot be used again until it is restored, which usually happens by finishing a long rest.

Spells and spell slots are distinguished by their spell levels. The higher the level, the more powerful the spell is. Therefore, the more powerful the spell slot needs to be. We’ll cover this in the next section.

A common mistake is thinking that spell levels and class levels are the same. This is not true. Instead, your class features table in the Player’s Handbook (PHB) details how many spell slots you have of each level.

Classes that access spell slots at Level 1 are full casters. These classes are bard, cleric, druid, sorcerer, and wizard. They gain the most spell slots and can access up to 9th level spell slots: the most powerful spells in the game.

Classes that access spell slots at Level 2 are half casters. These classes are paladin and ranger. Artificers are technically half casters despite having two spell slots at Level 1. Half casters gain up to 5th level spell slots.

Classes that access spell slots at Level 3 are third casters. These classes are the fighter subclass eldritch knight and the rogue subclass arcane trickster. They gain up to 4th level spell slots.

The exception to many of the rules we’ll discuss is the warlock class. This is primarily because their magical ability does not originate from the Spellcasting feature, but instead features such as Pact Magic and Mystic Arcanum.

Warlocks have spell slots. However, at any given warlock level, they are all the same spell level. For example, a 5th level warlock has two 3rd level spell slots. If they cast a 1st level spell, it is cast at 3rd level.

How Does Casting Spells at Different Levels Work?

As you gain levels in your class, you gain access to higher spell slots. To cast a spell, it must be powered by a spell slot of at least the same level as the spell.

For example, in order to cast the 3rd level spell Fireball, you must power it with an unused 3rd level spell slot or higher. A 3rd level spell can be powered by a 4th level spell slot since the power source is more than enough, but a 1st or 2nd level spell slot is not powerful enough.

Thankfully, many spells become more powerful when they are fueled by a higher-level spell slot. This is usually in the form of higher damage output or targeting additional creatures.

In the above example of Fireball, spending a 4th level spell slot to cast the spell adds another 1d6 damage to the spell’s damage. Any time there is a benefit to casting a spell at a higher level, it is detailed at the end of a spell’s description under the title: At higher levels.

If a spell description does not specify a difference when cast at a higher level, you are still able to cast the spell using that higher spell slot, but there are no additional benefits.

While a spell can be cast at a higher level, spell slots of different levels are not interchangeable. If you have two 2nd level spell slots, you cannot trade them in for one 4th level spell slot.


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Do Spell Slots Determine How Many Spells I Know?

Another common mistake that players make is conflating how many spells they know or have prepared with how many spell slots they have.

If you are playing a class that can cast spells, your class will have rules for how many different spells you have access to on any given day.

Bards, eldritch knights, rangers, arcane trickers, sorcerers, and warlocks have a column in their class table called Spells Known. This tells you how many different spells you have memorized and are now a part of your repertoire. When you go to cast a spell, it can only be one of the spells that you know.

Artificers, clerics, druids, paladins, and wizards have a certain number of spells that they can prepare for a day. This number is dependent on the level that you are in that class and the spellcasting modifier.

Both of these features determine the versatility of your spellcasting, giving you what you can choose from throughout your adventuring day. 

Spell slots determine the power of your spellcasting because they limit how many times in a day you can cast a spell and what level those spells are.

A druid who can prepare six spells might only have two spells slots. That means that they can only cast two spells throughout the day. And yes, you can cast the same spell more than once, as long as you have an unused spell slot for it.

My Best Metaphor

The best metaphor I have for how spell slots work is a vending machine that does not give change. The spells you know are the drinks on offer; your daily allowance is your spell slots. Buying a drink represents spending a spell slot. Some drinks cost $1, some $5, some $10, and so on.

You can’t buy a $5 drink with a dollar bill, but you can certainly use a fiver to buy a $1 drink. Again, no change will be refunded. Buy as many $1 drinks as you like, including multiples of the same beverage.

Where this breaks down is that you don’t get stronger drinks for more money, and you can’t save up the money between days.


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When Do I Get My Spell Slots Back?

All spent spell slots are restored at the end of a long rest. This is true for all spellcasting classes (warlocks get them back at short and long rests) and means that spell slots are a valuable resource to be managed throughout an adventuring day. 

If you use all your spell slots before breakfast, you’ll be waiting a long time before you can cast any spells again. At least you have cantrips to fall back on.

There are, however, exceptions to the rule. While wizards have Arcane Recovery to recover spell slots and sorcerers can spend sorcery points to create more spell slots, a warlock’s spell slots are all restored when they finish a short or long rest. 

You might think that seems unfair, but don’t worry—they also only have two spell slots until level 11.

What Spells Don’t Require Spell Slots?

Cantrips

Cantrips and ritual spells can be cast without using a spell slot.

They are minor magical effects—often called 0 level spells—and do not use spell slots when they are cast.

Ritual Spells

Ritual spells can be of any spell level and can be cast normally, spending a spell slot, or as a ritual without spending a spell slot. When casting a spell as a ritual, the time it takes to cast is extended by 10 minutes. 

For this to work, the spell must have the tag, “ritual”, and your class must specify that you can ritual cast. Since the spell does not use a spell slot, it can’t be cast at a higher level.

Traits and Abilities

There are also certain traits and abilities that allow players to cast spells without expending spell slots. In each case, it will specify when that ability is restored.

For example, Warlocks have access to Eldritch Invocations that allow them to cast spells without spell slots or material components. The invocation Fiendish Vigor allows them to cast the spell False Life without using a spell slot or material components.

Another example: a 5th level tiefling from the PHB can cast the spell Darkness once a day. 

Unless specified, casting a spell without using a spell slot still requires the necessary material components for the spell.


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How does Multiclassing Affect Spell Slots?

Okay, we’ve got a handle on how many spells each class can cast, when they are restored, and even what abilities allow you to cast spells without using spell slots. But what happens when you multiclass?

When you put levels into multiple classes with the Spellcasting feature, the number of spell slots that you have is determined by adding the class levels you have taken in different proportions.

Add together the levels of full casting classes you have taken, half the levels (rounded down) of half casting classes (rounded up for artificer levels), and a third (rounded down) of any levels in a third casting class.

For those that need a refresher:

Add the results, and then consult the Multiclass Spellcaster spell table below.

For example, how many spell slots would a character that is a level 8 cleric, level 7 paladin, and level 5 arcane trickster? (normally written: cleric 8 / paladin 7 / arcane trickster 5)

Clerics are full casters, so we count all 8 levels of cleric. 

Paladins are half casters, so we divide seven by two and round down to give us 3. 

Arcane tricksters are third casters, so we divide five by three and round down to get only 1.

8+3+1 gives us a total of 12, and our abomination of a multiclassed spellcaster has spell slots equal to a 12th level Multiclass Spellcaster: four 1st level, three 2nd level, three 3rd level, three 4th level, two 5th level, and one 6th level.

1st2nd3rd4th5th6th7th8th9th
1st2
2nd3
3rd42
4th43
5th432
6th433
7th4331
8th4332
9th43331
10th43332
11th433321
12th433321
13th4333211
14th4333211
15th43332111
16th43332111
17th433321111
18th433331111
19th433332111
20th433332211

Summary

Spell slots are the power source that is spent to cast spells.

  • Spell slots can be between level 1 and level 9; how many you have of each is determined by your class and character level.
  • To cast a spell, you need to use a spell slot of the same level or higher. When you do so with a higher spell slot, there can be additional benefits.
  • All spell slots are restored at the end of a long rest, although there are other abilities that can recover or create spell slots. Also, warlocks are the exception; they regain slots at any rest, including short.
  • Some features allow you to cast spells without using spell slots. Unless specified, they still require the material components.
  • When multiclassing, you combine the levels of your classes accordingly (see previous section) to determine how many spell slots you have of each level.

Now you can go forth and be a badass using your spells to their full potential. I hope that you always have spell slots available. Warlocks, enjoy your cantrips and short naps.

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