Dodge vs Dash vs Disengage in 5e

Dodge gives attacks against you Disadvantage until your next turn, Dash adds your Speed to your movement, and Disengage stops your movement provoking Opportunity Attacks. Most turns you attack or cast a spell. Some turns that is the wrong choice. The hero at 3 Hit Points, the Wizard with two goblins in reach, the scout who must reach the door first: each is better off spending the action on Dodge, Dash or Disengage. Here is what each one does, and the numbers on when it is worth it.

Dodge

If you take the Dodge action, you gain the following benefits: until the start of your next turn, any attack roll made against you has Disadvantage if you can see the attacker, and you make Dexterity saving throws with Advantage.

And the catch:

You lose these benefits if you have the Incapacitated condition or if your Speed is 0.

So a Grappled hero (Speed 0) gets nothing from Dodge. Break the grapple first.

Disadvantage means the attacker rolls two d20s and keeps the lower. Square the hit chance and you have the new one. A Goblin Warrior's Scimitar hits with +4; an Ogre's Greatclub with +6:

The higher your AC, the bigger the share Dodge cuts. At AC 12 a goblin lands a third fewer hits. At AC 18 it lands two thirds fewer. Critical hits almost vanish: both dice must show 20, a 1 in 400 chance instead of 1 in 20.

A worked case. A level 1 Wizard, AC 12, 8 Hit Points, two Goblin Warriors adjacent. Each Scimitar deals 1d6 + 2. If the Wizard attacks, the two goblins drop the Wizard this round 48.7% of the time. Dodging, 24.7%. With Mage Armor up (AC 15), 34.4% falls to 12.2%.

The Dexterity save half matters too. With +2 against a DC 13 save, a hero passes 50% of the time. Dodging, 75%.

Dash

When you take the Dash action, you gain extra movement for the current turn. The increase equals your Speed after applying any modifiers. With a Speed of 30 feet, for example, you can move up to 60 feet on your turn if you Dash.

Dash adds your Speed after penalties, so a slowed hero is still slow:

If your Speed of 30 feet is reduced to 15 feet, you can move up to 30 feet this turn if you Dash.

It works with other speeds too:

If you have a special speed, such as a Fly Speed or Swim Speed, you can use that speed instead of your Speed when you take this action.

Dash is for the turns where distance is the whole fight: reaching the lever before the portcullis drops, catching the cultist with the stolen idol, getting the unconscious Cleric's body out of the fire.

Disengage

If you take the Disengage action, your movement doesn't provoke Opportunity Attacks for the rest of the current turn.

An Opportunity Attack is what you risk when you walk away from someone with a sword:

You can make an Opportunity Attack when a creature that you can see leaves your reach using its action, its Bonus Action, its Reaction, or one of its speeds. To make the Opportunity Attack, take a Reaction to make one melee attack with a weapon or an Unarmed Strike against the provoking creature.

Being moved does not count:

You also don't provoke an Opportunity Attack when you Teleport or when you are moved without using your movement, action, Bonus Action, or Reaction.

Back to the Wizard. Walking out of reach of both goblins without Disengaging means two Opportunity Attacks: on average 7.5 damage at AC 12, 5.85 at AC 15. The Wizard has 8 Hit Points. Disengage costs a spell this turn; walking costs about the whole health bar. Next turn the Wizard is 30 feet away and casting.

Each enemy gets one Reaction per round, so walking past five goblins risks five swings.

The classes that do it as a Bonus Action

Spending your whole action on one of these is the price for most heroes. Two classes get them cheaper.

Rogue, level 2, Cunning Action:

On your turn, you can take one of the following actions as a Bonus Action: Dash, Disengage, or Hide.

A Rogue stabs and then walks off with no Opportunity Attack, every turn. That is why Rogues love fighting next to a Fighter: flank for Sneak Attack, then step back out of reach.

Monk, level 2, Focus Points:

Patient Defense. You can take the Disengage action as a Bonus Action. Alternatively, you can expend 1 Focus Point to take both the Disengage and Dodge actions as a Bonus Action.

Step of the Wind. You can take the Dash action as a Bonus Action. Alternatively, you can expend 1 Focus Point to take both the Disengage and Dash actions as a Bonus Action, and your jump distance is doubled for the turn.

For one Focus Point, a Monk punches and then Dodges in the same turn.

Goblins know this too

All three goblins in the SRD carry this line:

Nimble Escape. The goblin takes the Disengage or Hide action.

It is a Bonus Action. A Goblin Warrior slashes at your Fighter, Disengages, and runs back behind its friends with Shortbows, and your Fighter's Opportunity Attack never comes. Expect it. Close the gap with your own Dash, or bring a ranged weapon.

Which one, when

Dodge pays most when your AC is already high and the enemy hits hard. Disengage pays most when you are fragile and more than one enemy is next to you. Dash pays when the fight is a race.

For the rest of what fits in one turn, see your turn in combat, and for the attack you are dodging out of, Opportunity Attacks.

This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License.