D&D Proficiency Bonus Explained: What It Is and How It Works

26 March 2026

Your proficiency bonus is a flat number that gets added to rolls when you’re trained in something. It starts at +2 at level 1 and grows as you level up, eventually reaching +6 at level 17+.

It’s one of the few numbers that applies across attack rolls, saving throws, skill checks, and tool checks — making it one of the most versatile values on your character sheet.

Proficiency bonus by level

What proficiency applies to

You add your proficiency bonus to:

Attack rolls — when attacking with a weapon, spell attack, or unarmed strike you’re proficient with.

Saving throws — each class is proficient in exactly two saving throws, chosen at level 1.

Skill checks — for skills listed on your class (and any extra from your background or race).

Tool checks — if you’re proficient with a specific tool (thieves’ tools, alchemist’s supplies, etc.).

Spell save DC — the DC that enemies roll against to resist your spells uses your proficiency bonus: 8 + proficiency bonus + spellcasting modifier.

Spell attack bonus — your bonus to hit with attack roll spells: proficiency bonus + spellcasting modifier.

What proficiency does NOT apply to

Ability checks without proficiency. If you try to recall history without History proficiency, you just roll d20 + Intelligence modifier — no proficiency bonus.

Damage rolls. Proficiency never adds to damage, only to hit.

All saving throws. Only the two you’re proficient in get the bonus. Everything else is just d20 + ability modifier.

Expertise: double your bonus

Rogues and Bards get a feature called Expertise that doubles the proficiency bonus for chosen skills. At level 1 with +2 proficiency, Expertise gives +4 to that skill. By level 17 it’s +12.

A Rogue with Expertise in Stealth at high levels is nearly impossible to spot.

Other ways to get Expertise include the Skill Expert feat (any character) and Ranger (some subclasses).

Half proficiency: a special case

Some features say to add half your proficiency bonus (rounded down) to certain checks. A Bard’s Jack of All Trades feature does this — adding half proficiency to any ability check that doesn’t already include proficiency.

At level 1 with +2 proficiency, half is +1. At level 9 with +4, half is +2.

Weapon and armor proficiency

Proficiency with a weapon means you add your proficiency bonus to attack rolls with it. Without proficiency, you can still use the weapon but don’t add the bonus.

Armor proficiency is all-or-nothing. Without it, wearing the armor imposes severe penalties and you can’t cast spells in it.

Why this matters for new players

Most new players understand ability modifiers but underestimate the proficiency bonus. The difference between a proficient and non-proficient skill check is often the difference between success and failure on DC 15 checks.

When choosing a class, consider which skills and saving throws align with your playstyle — because you’ll be adding that proficiency bonus to them dozens of times per session.

And when you hit level 5, notice that your proficiency bonus jumps to +3. Combined with the extra attack that martial classes get at level 5, this is why “level 5” is often called the strongest power spike in D&D 5e.