How do you determine spellcasting ability?

If you’re sick of hitting monsters over the head, you can opt to sling spells at your opponents! However, spellcasting can get a little complicated, so let’s break down how spellcasting abilities are determined and what they’re used for.

A wizard casting a huge fireball (obviously they have high spell casting ability)


How do you calculate spellcasting ability?

Your spellcasting ability is determined by the class that the spell comes from and is usually between the choices of Intelligence, Wisdom and Charisma. Your Spellcasting ability modifier is then the same as your modifier for that attribute. So for example, a Wizard with an intelligence of 16 (+3) has a spellcasting ability modifier of +3.

Some subclasses of traditionally non-spellcasting classes will tell you the spellcasting ability in the relevant feature which grants it in the subclass. For example, the Eldritch Knight subclass for Fighters tells you to use Intelligence as your spellcasting ability in the ‘Spellcasting’ feature of this subclass.

For a full list of spellcasting abilities, see the table below:

Class Spellcasting ability
Artificer Intelligence
Bard Charisma
Cleric Wisdom
Druid Wisdom
Fighter (Eldritch Knight) Intelligence
Monk (Way of the four elements) Wisdom
Paladin Charisma
Ranger  Wisdom
Rogue (Arcane Trickster) Intelligence
Sorcerer Charisma
Wizard Intelligence
Warlock Charisma

If you are multiclassing, you do need to be careful about which spells come from which class, especially if they come from classes that use different spellcasting ability modifiers.

What is the spellcasting ability modifier?

The spellcasting ability modifier is the bonus you get to spells based on your spellcasting ability. It is simply equal to whatever your modifier for the spellcasting ability is. For example, a Bard with 16 Charisma has a +3 modifier to Charisma, so their spellcasting ability modifier is +3.

It is also possible to improve your spellcasting ability modifier in a number of ways, including increasing the attribute via ability score improvements, feats, magic items or effects, or more!

What are the uses of the spellcasting ability modifier?

The spellcasting ability modifier is used in a variety of ways. The main way is to determine both your spell attack bonus and spell save DC.

Calculating spell attack bonus in 5e

The spell attack bonus is the modifier you use when casting spells that require an attack roll, such as Firebolt and Guiding Bolt. If you see the text “spell attack”, then you’ll add this value to the roll. This is similar to how a martial character calculates their bonus to hit with a weapon. It is calculated with the following formula:

Spell attack bonus = Proficiency bonus + Spellcasting ability modifier.

For example, if our above Wizard with 16 Intelligence is level 4, the formula looks as follows:

Spell attack bonus = 2 (proficiency bonus) + 3 (spellcasting ability modifier) = 5

Calculating spell save DC in 5e

Spell save DC is used when you force another character to make a saving throw against an effect, such as casting Fireball or Cone of Cold. It is calculated with the following formula:

8 + proficiency bonus + spellcasting ability modifier.

Once again we can calculate our spell save DC for our level 4 wizard as follows:

8 + 2 (proficiency bonus) + 3 (spellcasting ability modifier) = 13

This means creatures will have to roll at least a 13 on their saving throw to pass the save against our wizard.

Some spells and features will allow you to add your spell attack modifier to the damage or healing of the roll, such as Cure Wounds which lets you heal for 1D8 + Spellcasting ability modifier (at level one).

How do you calculate other ability modifiers?

Ability modifiers are calculated based on the value of the chosen attribute. A table of corresponding values can be seen below:

Score Modifier
1 -5
2-3 -4
4-5 -3
6-7 -2
8-9 -1
10-11 0
12-13 +1
14-15 +2
16-17 +3
18-19 +4
20-21 +5
22-23 +6
24-25 +7
26-27 +8
28-29 +9
30 +10

An attribute of 20 is the maximum value a character can attain without the aid of magic items or special features, such as the Barbarian’s capstone, Primal Champion.

Some magical items, such as a Headband of Intellect which sets your Intelligence Score to 19, can override a character’s attribute value. In this case, you would use whatever value the item provides instead of your own. Do be careful to note down your base value as if you lose/take off the item your stats will go back to their original values!

A Headband of IntellectA Headband of Intellect can raise your Intelligence to 19, unfortunately, if you’re already smart it’s not going to help

Do you add proficiency to ability modifiers?

Proficiencies can be added depending on the situation. If you are proficient with a skill, tool or weapon you can add your proficiency bonus to the roll. So for example, if our level 4 Wizard has +3 to the Arcana skill, as it uses Intelligence. If they are also proficient in Arcana, this bonus goes to +5.

How does spellcasting work in 5e?

Spellcasting can be quite complicated when first approached, but it can be broken down into simple steps.

Spell splots and spell levels

Firstly, each caster has a certain amount of spell slots, depending on their class and level. You can find spell slot amounts on the class pages of the Player’s Handbook (PHB), and for multicasting, the rules can be found in the multiclassing section of the PHB on page 165.

You then have your spells, each of a level between 0 (cantrips) and 9. Depending on your class and spellcasting ability modifier, you can prepare a certain number of spells to have access to during that particular day (you can change out your prepared spells at the end of a long rest).

I like to envision a character’s spell slots of buckets, each of a different size getting larger as the level of the spell slot increases. The spells can then be seen as balls of varying sizes in a similar fashion. When you cast a spell, you have to put it in a spell slot that is at least equal to the spell’s level, or higher. This means you can’t put one of the balls into a bucket that is smaller than it, but you can put it in one that is the same size or larger. Sometimes you can get a bonus if you ‘upcast’ a spell, that is to put the ball in a larger bucket. These bonuses can range from extra damage, duration, or number of targets.

Cantrips can be cast without limitation (i.e. an infinite number of cantrip buckets), but they cannot be upcast for extra benefits. Instead these increase in effectiveness as a character gains levels.

These spell slots then fully refresh at the end of a long rest.

Warlock spell slots

Warlocks act a little differently, with only a few spell slots, all of the same level (refer to the Warlock class section to see the scaling). When a Warlock casts any levelled spell, it will automatically upcast to the level of the Warlock’s spell slots. For example, a level 5 Warlock has two spell slots each of level 3. So casting any spell, such as Hex, would automatically cast at level three.

To compensate for the lower number of slots, a Warlock refreshes all spell slots after a short rest, as well as the end of a long rest.

What’s the best spellcasting class in DnD 5e?

It’s difficult to determine the ‘best’ spellcasting class in Dnd 5e, as each class tends to aim towards a different toolset.

For example, Wizards have by far the biggest spell list, meaning they can choose from a wide array of options when deciding what to learn, however, they have no spells that let them heal themselves or their allies in any way. Whereas Sorcerers have more restrictions, but their class allows them to specialise on the spells they do get by making them faster, more subtle or even changing damage types.

The cleric is often regarded as a very good spellcasting class, as they are highly variable between damage, healing, utility and support. A personal favourite of mine is the Paladin, who predominantly focuses on damage and buff spells, to enhance their own attacks and make them stronger in direct combat.

Venture forth!

I hope this has helped clear up the foggy cloud that spellcasting can be. Now get out there and blast your foes with the correct modifiers, see enemies crippled by your spells as they fail against your newly calculated spell save DC and most importantly, have fun building your master of the arcane!

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A big dnd and gaming fan in general, if I'm not rolling dice I'm probably watching/playing LoL or some form of RPG (currently Baldur's Gate 3). Around the table you'll most likely find me as a paladin or a rogue, I love rolling lots of dice and getting big damage totals!