What is Ability Score Improvement in D&D 5e? (And How Does It Work)

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When your Character reaches Levels 4, 8, 12, 16 and 19, they gain an Ability Score Improvement (ASI).

And this ability score improvement is just what it sounds like: an opportunity to raise your ability scores. These are Strength, Dexterity, Constitution, Charisma, Wisdom, and Intelligence.

With your ASI you can take either +1 in two of these scores, or +2 in one of these scores (a bit confusing at first read, I know).

And a couple of classes (like fighters and rogues) get ASIs at other levels as well.


Ability Modifiers

Each ability score has a modifier.

For example, having a 16 in an ability score gives you a +3 modifier for that score.

The modifier is much more important than the actual ability score.

Here’s a breakdown:

Ability Score Modifier
6–7 −2
8–9 −1
10–11 +0
12–13 +1
14–15 +2
16–17 +3
18–19 +4
20–21 +5

As you can see, the modifier goes up by +1 when an ability score reaches an even number, but it does not change when you increase from an even number to an odd number.

So improving any ability score by +2 will only increase your modifier by +1.


How do you know when to boost an ability score?

If your primary class ability score is less than 20, you should consider increasing your ability score.

A list of the primary abilities by class is shown at the end of this article.

In 5e, characters usually cannot raise their ability scores over 20.

Also it is much better to have an even-numbered score than an odd-numbered score in 5e. So raising your Dex from 15 to 17 is (usually) a partial waste of an ASI. It’s better to increase your Dex to 16 and use the other +1 for a different ability score.

Similarly, if your Dex is 16 it usually doesn’t make sense to increase it to 17. Either increase it to 18 or don’t increase it yet.


Feats and Half-Feats

Feats are an optional rule in 5e.

If your group is playing with the feats, you’re allowed to choose a feat instead of an ASI. In some cases it’s better to take a feat than an ASI, but in some cases it’s not. There are also a number of “half-feats” that give you a +1 bonus to an ability score and also grant you another power or powers.

These are definitely worth considering if you only need +1 to an ability score to reach an even number.

For example, if your Dex is 15 and you want to raise it to 16, you can take a feat that gives you a +1 bonus to Dex and also gives you another power.

Occasionally there may be times when you want to increase an attribute to an odd number.

This is usually because (a) you’re planning to take a half-feat in the future, (b) you need an ability score to be 13 in order to multi-class, or (c) you need a certain strength to wear heavy armor without a movement penalty.


When is a feat better to take than an ASI?

This depends on your character build, and perhaps your DM’s world.

Some characters need feats more than others.

Fighters in particular are encouraged to take feats because they get extra ASIs. There are certain feats that can be really useful or powerful to some characters. You should read about your feat options before making a decision.

For example, a player reaches level 4 and wants to gain more hit points with their ASI.

1. They could take +2 Con, raising their constitution modifier by +1, giving them 1 extra hit point per level (+4 hp total because they’re level 4), in addition to the hp they gain for reaching level 4. This would also increase their Con saving throws by +1.

2. Or the player could take the Toughness feat and gain +2 hp per level (+8 hp total), but they wouldn’t gain the +1 modifier or the bonus to Con saving throws.

3. Or the player could improve their dexterity, or take a defensive feat that would make them harder to hit in combat, so their hp would last longer.


What is “Bounded Accuracy?”

Bounded accuracy is a term to describe a game design technique that puts limits on the bonuses that characters get in 5e.

Essentially, even if you don’t give yourself bonuses to certain abilities or skills, you can still be successful at using those abilities or skills if you roll well.

Obviously it might be nice to have high scores in every ability.

But really the game isn’t designed for that.

Even high-level players won’t be skilled at everything. For this reason, you don’t need to maximize every ability score, and you’re often OK if taking a feat instead of an ASI.

Also, sometimes it takes away from the fun if your character is good at everything.

D&D is a collaborative game where players work together and fill in for each others’ weaknesses. And failure can lead to crazy-fun antics or epic role-playing moments.

What I’m saying is, you don’t have to be good at everything, and you probably shouldn’t be!


Multiclassing: When do you get an ASI?

Like with feats, multiclassing is an optional rule in 5e.

If you multiclass, it will affect the rate at which you get an ASI.

You only get an ASI when you reach a certain level in each class.

For example, a fighter 1, wizard 3 would not get a feat until they take a 4th level of wizard or reach fighter 4.

This may mean that your multi-classed character has to wait longer than other characters to earn an ASI.


What does an ASI give you?

The benefits depend a lot on your class and your existing ability scores.

A +1 to modifier might seem boring compared to a feat. But often it’s a bigger bonus than you realize.

However, you also need to look at your character’s abilities and see what the different options actually give you, and you need to decide on which option feels most fun.

For example:

Suppose that a wizard raises their Dex from 16 to 18. They get +1 to AC and initiative. Since they don’t usually use weapons or sneak around, the other benefits aren’t very noticeable.

Now suppose that a rogue raises their Dex from 16 to 18. Like the wizard, they get +1 to AC and initiative, but they also get a +1 to hit, +1 damage, +1 to all dexterity skill and tool checks (acrobatics, picking locks, stealth, slight of hands), which they use quite often.

If the wizard takes a +2 to Int (+1 modifier), they can prepare an extra spell each day, gain +1 bonus to Int skill checks, and most importantly their spell attack rolls and the DC of their spells goes up by +1. This means they will become better casters, more likely to hit enemies, and enemies will be more likely to fail saving throws against the wizard’s spells.

If the rogue takes +2 to Int, they probably don’t get any noticeable benefits other than learning one additional language.

Let’s look at the rogue again and their combat abilities.

A +1 Dex modifier might look like a 5% improvement to all d20s rolls, but math shows that it often is much more. Exact numbers depend on the enemy you’re facing, but let’s look more closely at a Level 4 rogue as an example:

Rogue w/ feat and no ASI Rogue w/ ASI (+2 to Dex)
16 dexterity (+3 modifier) 18 dexterity (+4 modifier)
Weapon attack is +5 Weapon attack is +6
Damage is d6+3 + 2d6 from sneak attack (ave 13.5) Damage is d6+4 + 2d6 from sneak attack (ave 14.5)
55% chance to hit an enemy with AC 16 60% chance to hit an enemy with AC 16
Average damage per round = (0.55)(13.5) = 7.425 Average damage per round = (0.6)(14.5) = 8.7
This is a 17% increase in damage!
Average damage done to you by the enemy might be 13 points with a 50% change to hit.
Average damage taken per round = (0.5)(13) = 6.5
Average damage done to you by the enemy might be 13 points with a 45% change to hit because you have higher AC.
Average damage taken per round = (0.45)(13) = 5.85
This is a 10% decrease in damage taken per turn
+5 to Dex skill checks +6 to Dex skill checks
This is a 5% improvement on all Dex skills checks

In this example above, a 5% bonus to your roll results in a 17% increase in the damage you do, a 10% decrease in the damage you take, and 5% improvement in all Dex skills.

ASIs might seem boring, but they can be pretty powerful at times.

Now obviously the rogue on the left has a feat the gives them extra abilities or bonuses, and that can be quite powerful. But you have to examine those benefits to decide if they’re worth giving up an ASI.

In short, don’t overlook the benefits of taking an ASI. But also keep your mind open about taking a feat instead.

Just note if you take an ASI, you should focus on the primary abilities for your character.

Here’s a brief chart of the primary abilities for each class, but keep in mind they can vary for individual characters that you build.

Artificer Intelligence
Barbarian Strength
Bard Charisma
Blood Hunter Strength or Dexterity & Intelligence
Cleric Wisdom
Druid Wisdom
Fighter Strength or Dexterity
Monk Dexterity & Wisdom
Paladin Strength & Charisma
Ranger Dexterity & Wisdom
Rogue Dexterity
Sorcerer Charisma
Warlock Charisma
Wizard Intelligence
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