Concentration in D&D 5e, Explained
A plain-English rules guide
Concentration is one of the most-forgotten rules at the table — and one of the most important, because it's the main thing keeping powerful spells in check. Here's what it is, what breaks it, and the saving throw formula everyone fumbles.
What is concentration?
Some spells require concentration to keep them going, shown by "Concentration" in the spell's duration. While you concentrate on a spell, you maintain its effect for up to the listed duration. The catch: you can only concentrate on one spell at a time.
What breaks concentration?
Your concentration ends — and the spell ends with it — if any of these happen:
- You cast another spell that requires concentration. The new spell replaces the old one; you can't hold two at once.
- You take damage and fail a Constitution saving throw (see the formula below).
- You are incapacitated or killed.
- An environmental effect the DM rules would break it (like being knocked prone by a wave), which may call for a check.
You can also choose to end concentration voluntarily at any time (no action required).
The concentration saving throw
This is the part people get wrong. Whenever you take damage while concentrating, you must make a Constitution saving throw to maintain the spell. The DC is:
DC = 10, or half the damage taken, whichever is higher. Take 18 damage? Half is 9, which is below 10, so the DC is 10. Take 30 damage? Half is 15, so the DC is 15. The "half the damage" part only starts to matter once you take 21+ damage in one hit.
You make a separate save for each instance of damage. If you're hit by two attacks, that's two saves. Fail one, and the spell ends.
Common questions
No — only if you fail the Constitution save. Take the damage, roll a Con save against the DC (10 or half the damage, whichever is higher), and the spell continues on a success.
Yes. Casting a spell that doesn't require concentration is fine and doesn't break your existing concentration.
Proficiency in Constitution saves, a high Con modifier, and features like War Caster (advantage on concentration saves) all make you far more reliable.
This guide explains the rules in our own words as a reference aid, drawing on the D&D 5e SRD (CC BY 4.0). Always confirm details against your own rulebooks for anything rules-critical.
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