How do you do damage in D&D? What dice do you use and how do you know how much damage you've done after rolling the dice? When it says 1d10 does that mean you did one damage or ten?
To deal damage, you roll X amounts of Y-sided dice, usually annotated with XdY. For example:
- 2d6 means you roll two 6-sided dice.
- 3d8 means you roll three 8-sided dice.
- 1d12 means you roll one 12-sided dice.
If you attack with a weapon, find your weapon's damage dice on the weapon damage table, on PHB pg. 149. For example a dagger's damage dice is d4.
If you deal damage with a spell or other effect, the description will tell you what dice to roll and how many. For example frostbite cantrip's damage dice is d6 (it becomes 2d6 at level 5, 3d6 at level 11, and finally 4d6 at level 17).
Add all the damage dice and the modifiers-taking into account reduction, resistance, vulnerability, and immunity, then subtract the remaining damage from the target's health point.
There is an entire section on PHB, pg. 196, "Damage and Healing". A section specifically deals about "Damage Rolls".
Each weapon, spell, and harmful monster ability specifies the damage it deals. You roll the damage die or dice, add any modifiers, and apply the damage to your target. Magic weapons, special abilities, and other factors can grant a bonus to damage.
When attacking with a weapon, you add your ability modifier—the same modifier used for the attack roll—to the damage. A spell tells you which dice to roll for damage and whether to add any modifiers.
If a spell or other effect deals damage to more than one target at the same time, roll the damage once for all of them. For example, when a wizard casts fireball or a cleric casts flame strike, the spell’s damage is rolled once for all creatures caught in the blast.
Each attack or reference to damage (and many other things) will indicate the dice roll in the format: XdY.
For example: 3d6 or 1d10 or 2d8.
The first number is the number of dice you roll. The second number is the type of dice you roll.
- 3d6 means you roll three 6-sided dice.
- 1d10 means you roll one 10-sided dice.
- 2d8 means you roll two 8-sided dice.
Once you have rolled the dice, add them up to get the total.
Sometimes you will see additional modifiers to the dice roll.
For example: 1d10 + 6, or 2d6 + Strength modifier.
Once you add these modifiers to your dice roll, the final total is the damage.
The damage is removed from the opponent's hit points.
This is all covered in the Player's Handbook