Weapon damage is written in dice notation as weapon die + ability modifier. A two-handed greatsword wielded by a fighter with 18 Strength (+4) deals 2d6+4 — an average of 7 + 4 = 11 damage per hit. Add other flat riders (a Rage bonus, Dueling style, Hunter’s Mark) to the same total.
Critical hits double the dice, not the modifier. That greatsword crit is 4d6+4, averaging 14 + 4 = 18 damage — you roll the weapon’s damage dice twice and add your modifier once.
Resistance halves the total (rounding down), vulnerability doubles it, and immunity reduces it to 0. Apply resistance last, after all dice and modifiers are summed: 18 damage against a resistant target becomes 9.
To weigh build choices, players compare DPR (damage per round): multiply your average hit by your chance to hit, then add expected crit damage across all your attacks. A feat like Great Weapon Master trades accuracy for a large flat bonus — note that it requires a Heavy weapon (greatsword, greataxe, maul), so it does not work with a longsword. The 2014 and 2024 versions of the feat work differently, so check which edition your table uses.
Average damage and DPR
Every die averages half its maximum plus 0.5: a d6 averages 3.5, a d8 4.5, a d12 6.5. So the average of NdX+M is N × (X+1)/2 + M — 2d6+4 averages 11. DPR (damage per round) weighs that average against your chance to hit: at a typical 65% hit chance, a 1d8+4 attack is worth 0.60 × 8.5 from normal hits plus 0.05 × 13 from crits — 5.75 DPR. Compare per-die averages side by side with the dice roller.
Attack rolls and hit chance
An attack hits when d20 + ability modifier + proficiency bonus meets the target's AC. Your hit chance is (21 + attack bonus − AC) × 5%, clamped between 5% and 95% — a natural 20 always hits and crits, a natural 1 always misses. A +5 attack against AC 15 hits 55% of the time. Advantage is worth roughly +3 to the attack bonus and matters most against mid-range ACs. Sizing up a whole fight rather than one swing? Weigh it with the encounter difficulty calculator.
Fall damage and save-for-half spells
Falling deals 1d6 bludgeoning damage per 10 feet, capped at 20d6 — a 30-foot drop averages 10.5 damage, and any fall of 200 feet or more averages 70. Spells that allow a saving throw usually deal half damage on a success: a fireball's 8d6 (average 28) still burns for 14 through a successful Dexterity save. Cantrips scale with character level, adding a damage die at levels 5, 11, and 17.