Mastering the Mechanics: How to Cast Fireball Twice on Your Turn

It’s time to throw your whole spellbook out the window because chances are that everything you thought you knew about casting two spells on the same turn is wrong. Get ready to cast feather fall because we’re going to take a deep dive off the cliff of D&D rules minutia.

Many 5th Edition players know that you can’t cast fireball as an action and misty step as a bonus action on the same turn—but you can cast sacred flame as an action and healing word as a bonus action. This is commonly understood as, “If you cast two spells on the same turn, one of them has to be a cantrip.”

But that’s not actually what the rules say. Jeremy Crawford, the lead rules designer of D&D, recently answered some questions on Twitter about bonus action spellcasting that made me realize I’d been completely misunderstanding this rule, mostly because I thought that the part about casting times was totally obvious and that I didn’t need to read it closely.

True, this section starts out by stating the obvious, but it hides one of the most subtle and unrecognized nuances of the entire 5th Edition ruleset.

Most spells require a single action to cast, but some spells require a bonus action, a reaction, or much more time to cast. […] A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven’t already taken a bonus action this turn. You can’t cast another spell during the same turn, except for a cantrip with a casting time of 1 action.

This rule means that you can’t cast fireball and misty step on the same turn as we noted above. Similarly, if you’re a sorcerer using Quickened Spell, you can’t cast fireball as an action and then spend 2 sorcery points to cast another fireball as a bonus action. This rule is a way to limit the power of what a spellcaster can accomplish in a single turn since combining some spells on the same turn could have devastatingly powerful effects that upset any notion of balance. For example, if this rule didn’t exist, a cleric could cast guiding bolt as an action and then cast spiritual weapon, making an attack against the same target with advantage as a bonus action. Casting both of these spells in the same turn is an order of magnitude more powerful than casting them over the course of two rounds.

Note that the design philosophy behind this rule doesn’t attempt to handle edge cases that arise from multiclassed characters; multiclassing is considered an optional rule that doesn’t factor into the balance of the core game system.

For people who have been playing 5th Edition for a while, none of this is anything new. The subtle part here is that there is no rule that says you can’t cast two non-cantrip spells on the same turn.

Let me state that again: there is no rule anywhere in 5th Edition that bans you from casting more than one spell of 1st level or higher on the same turn. There’s an additional restriction when casting a spell as a bonus action as described above, but the limiting factor on spellcasting is actually the fact that you only have one action per turn and at most one bonus action per turn. (Recall that you don’t necessarily have a bonus action on your turn unless you have a specific ability, spell, or feature to use as a bonus action.) It’s also worth noting that spells with a casting time of 1 bonus action can only be cast as a bonus action; you can’t ever perform a bonus action with your regular action, so casting misty step twice on the same turn is never possible.

Let’s go over some examples to clarify how the rules around spellcasting and bonus actions interact.

Example 1. You’re a 1st-level wizard who knows the mage hand, light, and ray of frost cantrips. You have burning hands, charm person, mage armor, and magic missile prepared. All of your spells require an action to cast, so the bonus action spellcasting rules don’t matter for you.

Example 2. You’re a 3rd-level cleric, and you cast spiritual weapon (a 2nd-level spell) as a bonus action. If you wish to cast another spell during your turn, it must be a cantrip with a casting time of 1 action (such as sacred flame).

Example 3. You’re a 3rd-level sorcerer, and you’re caught unprepared! You cast fire bolt (a cantrip with a casting time of 1 action) with your action to protect yourself and then use Quickened Spell to cast mage armor (a 1st-level spell) as a bonus action.

Example 4. You’re a former soldier who didn’t read the fine print on a fiendish contract, so you’re now a 2nd-level fighter and 5th-level warlock. You can cast fireball (a 3nd-level spell) as an action and then use Action Surge to take an additional action and cast fireball again. Since you aren’t casting a spell with a bonus action, the bonus action spellcasting rules don’t affect you. (Even without multiclassing, eldritch knights may face similar situations with their War Magic and Improved War Magic features.)

The 5th Edition rules are generally pretty elegant, but cases like this can be really complicated. As a GM, feel free to throw out all of the examples above and interpret the rules in the way that makes you and your players happiest! You can let your players ignore the bonus action spellcasting rules and feel powerful by pulling off huge combos, though the non-spellcasting party members may feel a little put out if all the enemies are gone before they get to do anything.

Leave your comments and questions below, and feel free to request other topics to be covered in the Mastering the Mechanics series!

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This article was updated on December 20th. The original version stated that as a 3rd-level sorcerer you can cast mage armor as an action and then use Quickened Spell to cast fire bolt as a bonus action, which is incorrect because, if you cast two spells in a turn, one of them must be a cantrip with a casting time of 1 action. Of course, it’s functionally the same, but we strive for complete correctness while being nitpicky about rules in the first place.