Can I use a cantrip as an action and bonus action?

The answer to whether you can use a cantrip as an action and bonus action is yes, but with certain limitations and conditions, as the rules in the Player’s Handbook (PHB) clearly state that if a spell is a bonus action, you may cast a cantrip as an action, and vice versa. The key is understanding the spells’ casting times and the actions available to you in a turn, which dictates how you can combine cantrips with other spells or attacks.

Frequently Asked Questions

General Cantrip Rules

1. Can you cast two cantrips in one turn if one is a bonus action? Yes, the rule for casting any spell with a bonus action says that the only other spells you may cast that turn are cantrips with an action.
2. Can you cast a cantrip and a bonus action attack? You can certainly cast a bonus action spell, and then use your action to cast a cantrip, but casting a cantrip with a casting time of “1 bonus action” should still trigger the normal limitations for bonus action spells.
3. Can you use Eldritch Blast as a bonus action? It’s good to have, not really mandatory; you can already cast Eldritch Blast as a bonus action for 5 rounds, and that’s without converting any spell slots.

Cantrips and Concentration

4. Can you cast Cantrips while Concentrating on a Spell? Yes, you only break concentration if you cast another spell that requires concentration.
5. Does a cantrip break invisibility? Invisibility only breaks if you attack or cast a spell, so, RAW, you should be able to use it and stay Invisible.

Combining Cantrips with Other Actions

6. Can you cast 2 cantrips if you have 2 attacks? They can cast a cantrip in replacement of an attack that they take during the Attack action, but only one; they can’t do two cantrips in the same action.
7. Can you use extra attack on a cantrip? No, you either use your action to cast a spell/cantrip or you use it to attack with your weapons and get your extra attacks.
8. Is booming blade better than 2 attacks? Booming Blade does better compared to non-Fighter martial characters who get less attacks, nearly matching the damage output of 2 attacks at 11th level without secondary damage and eventually surpassing it at 17th level.

Specific Cantrip Abilities

9. Can you use Eldritch blast twice with extra attack? No, the fighter gets its extra attack from taking the Attack action, and Eldritch Blast is the cast a spell action.
10. How many times can you use a cantrip per day? As a Sorcerer, you know 5 cantrips, and you can cast each of those 5 as many times as you want per day.
11. Can cantrips be cast infinitely? Yes, cantrips can be cast an unlimited number of times per day without using up a spell slot.

Advanced Spellcasting

12. Can you cast 2 spells in a turn 5e? You can’t cast another spell during the same turn, except for a cantrip with a casting time of 1 action.
13. Can you quicken Eldritch blast? Yes, at level 7, accounting for AC and assuming the character is min-maxed to have 20 CHA, a Quickened Agonizing Eldritch Blast deals significant damage.
14. Can you counterspell a counterspell? Yes, you can counterspell a counterspell cast against you, as addressed in the Sage Advice Compendium.

Cantrip Limitations and Variations

15. Can you unlearn cantrips? No, there is no way to change cantrips in all classes; once you’ve chosen a cantrip, you never change it, although there’s a UA rule variant that gives the option to swap one cantrip within the “swap 1 spell at level up” feature for all spellcasters.