D&D 5e Hit Chance & DPR Calculator
Assumptions: natural 1 always misses; rolls in your critical range are treated as critical hits; critical hits double damage dice from your normal hit expression but not flat modifiers.
How this D&D 5e combat calculator helps
Combat in Dungeons & Dragons 5e often comes down to probability. You might feel like your build is strong, but a quick damage-per-round (DPR) check can reveal whether your strategy is actually consistent. This calculator estimates your expected damage by combining hit chance, crit chance, attack count, and average dice damage.
Instead of rolling dozens of test rounds manually, you can plug in your attack bonus, target Armor Class, and damage expression to get immediate numbers. It is useful for fighters comparing weapon styles, rogues testing advantage setups, paladins estimating burst rounds, and Dungeon Masters balancing encounters.
What the calculator computes
1) Hit probability
The tool calculates your chance to land a normal hit and your chance to crit. It supports:
- Normal rolls (1d20)
- Advantage (highest of 2d20)
- Disadvantage (lowest of 2d20)
- Custom crit ranges such as 19–20
2) Average damage on hit and crit
Enter damage using dice notation such as 1d8+4, 2d6+3, or 1d10+1d6+5. On a critical hit, all dice in your normal hit expression are doubled automatically, while flat bonuses stay the same. You can also add a separate “crit-only” expression for effects that trigger only on crit.
3) Expected DPR
Expected damage per attack is:
(normal hit chance × average normal hit damage) + (crit chance × average crit damage)
That value is multiplied by your attacks per round to produce total DPR.
4) Optional rounds-to-defeat estimate
If you provide target HP, the calculator estimates average rounds to drop that enemy: Target HP ÷ DPR. It is not a guarantee, but it gives a strong planning baseline.
Dice notation quick guide
- 1d8+4 = one eight-sided die plus 4
- 2d6+3 = two six-sided dice plus 3
- 1d10+1d6+5 = mixed dice plus a flat bonus
- 2d6-1 = supports subtraction too
For “crit-only” damage, add only dice or modifiers that should apply on critical hits in your rules context.
Practical build testing ideas
Compare weapon options
Try the same attack bonus and AC while switching damage from 1d8+4 to 2d6+4. You can quickly see whether average damage changes enough to matter over many rounds.
Measure the value of advantage
Change roll type from Normal to Advantage. You will notice hit chance and crit chance both increase, especially against higher AC enemies. This helps evaluate class features and teamwork tactics that generate advantage.
Model crit-focused builds
Lower crit range from 20 to 19 and add crit-only damage. This can approximate builds that spike hard on crits and helps determine whether crit fishing improves overall consistency.
Interpreting results at the table
- High DPR, low consistency: Burst-focused builds can feel amazing but swingy.
- Moderate DPR, high hit chance: Reliable damage is often better in long fights.
- Rounds to defeat: Great for encounter pacing and resource planning.
- At least one crit chance: Helpful for builds with strong crit riders.
Limitations and assumptions
This is a streamlined combat math tool, not a full encounter simulator. It does not automatically account for:
- Resistances, immunities, and vulnerabilities
- Saving throw based damage
- Conditional riders (once per turn, resource limits, etc.)
- Changing AC or buffs/debuffs across rounds
Still, for fast damage comparisons and decision support, this kind of D&D 5e combat calculator is extremely effective.
Final thoughts
Whether you are optimizing a character, balancing monsters as a DM, or just curious how your combat choices stack up, expected-value math gives you clarity. Use this calculator before a session, test a few scenarios, and bring smarter tactical decisions to your next encounter.