How initiative works
When a fight starts, the Dungeon Master says "roll for initiative" and everyone rolls a Dexterity check: a d20 plus their Dexterity modifier. The Dungeon Master usually rolls once for each group of identical monsters, so all the goblins act together. Then everyone acts from highest to lowest, and that order holds for the whole fight.
Set your modifier with the stepper above and roll. With a Dexterity modifier of +4 that is 1d20+4: anything from 5 to 24, 14.5 on average, and a 50% chance of 15 or more.
Your odds of going first
Each point of bonus you have over someone is worth about 4.5% more chance of acting before them. Your edge is your initiative bonus minus theirs; the last column is the same roll with advantage:
| Edge | First | Tie | Adv. |
|---|---|---|---|
| -5 | 26.25% | 3.75% | 39.81% |
| -3 | 34% | 4.25% | 49.3% |
| -1 | 42.75% | 4.75% | 59.14% |
| 0 | 47.5% | 5% | 64.13% |
| +1 | 52.5% | 4.75% | 69.13% |
| +3 | 61.75% | 4.25% | 77.69% |
| +5 | 70% | 3.75% | 84.5% |
"First" means a strictly higher total; ties are the next column. Advantage is worth more than a +3 edge and close to +4. The dice calculator works out any other roll.
Ties
In the SRD 5.1 rules, the Dungeon Master decides the order between tied monsters, players decide the order between their own tied characters, and the Dungeon Master can decide when a monster ties with a player character. Many tables break ties by the higher Dexterity score instead.
Going first more often
- A higher Dexterity is the plain way: every +1 modifier is about +4.5% to beat a given foe.
- Advantage on initiative, like a 7th-level barbarian's Feral Instinct, means rolling two d20s and keeping the higher: from 47.5% to 64% against an equal foe.
- Half proficiency. Initiative is a Dexterity check, so a bard's Jack of All Trades and a Champion fighter's Remarkable Athlete add half your proficiency bonus to it.
- Flat bonuses add straight to the roll: a +5 lifts your chance of beating an equal foe from 47.5% to 70%.
Surprise
A surprised creature still rolls initiative, but cannot move or take an action on its first turn, and cannot take a reaction until that turn ends. Rolling high when surprised still sets your place in later rounds.
Questions
How do you roll for initiative in D&D?
Roll a d20 and add your Dexterity modifier. That is a Dexterity check, so anything that adds to Dexterity checks adds to it too. Everyone acts from the highest total to the lowest, and the order stays the same for the whole fight.
What dice do you roll for initiative?
One d20, plus your Dexterity modifier. With +2 Dexterity that is 1d20+2; with +4 it is 1d20+4, which lands from 5 to 24 and averages 14.5.
Who goes first if initiative is tied?
In the SRD 5.1 rules the Dungeon Master orders tied monsters, players order their own tied characters, and the Dungeon Master decides a tie between a monster and a player. Many tables use the higher Dexterity score as a tiebreaker. Two creatures with the same bonus tie 5% of the time.
Can you roll initiative with advantage?
Yes, when a feature gives it, like the barbarian's Feral Instinct at 7th level. Roll two d20s, keep the higher, add Dexterity. Against a foe with the same bonus your chance of going strictly first rises from 47.5% to 64.1%.
Does the DM roll initiative for every monster?
Usually the Dungeon Master rolls once for each group of identical creatures, so a pack of wolves all act on the same count. Different monsters each get their own roll.
Is this initiative roller fair?
Yes. The d20 comes from your browser's cryptographic random number generator, with no bias towards any face, so every roll is an independent, even 1 to 20 before your modifier.