D&D 5e Attack Roll Calculator
Estimate hit probability and average damage of a Dungeons & Dragons 5e attack from attack bonus, target AC, damage dice and modifier.
How to Use the D&D 5e Attack Roll Calculator
- Enter your attack bonus and the target AC.
- Enter the number of damage dice, die size and flat damage modifier.
- Click Calculate.
使用场景
- •Character optimisation.
- •Encounter balancing for DMs.
- •Explaining dice math to new players.
公式
Hit % = (21 − (AC − attack bonus)) / 20 × 100, clamped 5–100 (natural 1 always misses, natural 20 always hits). Average damage = N × (die_max + 1)/2 + modifier.
常见问题
Why clamp at 5 and 100?
5e rules say a natural 1 always misses and a natural 20 always hits, so the probability is bounded in [5, 100]%.
Does this handle critical hits?
The average here is per normal hit; on a crit, only the dice double, not the modifier. Multiply the dice portion by 2 for a crit average.