How to Calculate Crit Chance and Damage

Every game with critical hits hides the same two numbers behind different names: how often a hit crits, and how much harder a crit lands. Learning to calculate both turns a vague stat block into a real damage estimate. The math is the same whether you play an RPG, a MOBA, or roll dice across a tabletop battlefield, because crit chance and crit damage are just probability and multiplication wearing different costumes.

What Is Crit Chance and What Is a Crit Damage Multiplier?

Crit chance is the probability that a given attack lands as a critical hit instead of a normal hit, expressed as a percentage. A 20% crit chance means roughly one attack in five crits, while the other four land as ordinary hits at normal damage.

Crit damage multiplier is the factor applied to base damage once a hit crits. A 2.0x crit multiplier doubles the damage of that single hit compared to a normal hit; a 1.5x multiplier adds half again as much damage.

Some games display crit damage as a bonus percentage rather than a multiplier, such as “+50% crit damage.” That bonus percentage converts to a multiplier by adding it to 1.0, so +50% crit damage equals a 1.5x multiplier, and +150% crit damage equals a 2.5x multiplier.

These two stats answer different questions. Crit chance controls how often the bonus damage applies. Crit multiplier controls how large that bonus is on the hits where it does apply. Neither number alone tells you the real damage output of a build; you need both together.

How Do You Calculate Expected Damage From a Crit?

Expected damage blends the normal-hit outcome and the crit outcome into one average number. The formula is: expected damage = base damage x (1 + crit chance x (crit multiplier – 1)).

Breaking the formula down helps it make sense. “Crit multiplier – 1” isolates the extra damage a crit adds on top of a normal hit. Multiplying that extra amount by crit chance spreads it across every attack, since only a fraction of attacks actually crit. Adding 1 back in restores the guaranteed base damage every hit deals regardless of outcome.

A concrete pass through the numbers: base damage 100, crit chance 25% (0.25), crit multiplier 2.0x. The extra crit damage is 2.0 – 1 = 1.0. Multiply by crit chance: 0.25 x 1.0 = 0.25. Add 1: 1.25. Multiply by base damage: 100 x 1.25 = 125 expected damage per attack.

This average number matters for comparing gear and builds, because a single crit roll swings wildly while the long-run average stays predictable. A weapon that hits harder but crits less often can still lose to a weapon with a smaller multiplier and a higher crit chance, and the formula is the only reliable way to tell which one wins.

Do Crit Chance and Crit Damage Stack the Same Way?

No, crit chance and crit damage typically stack by different rules, and mixing them up leads to bad build math. Crit chance sources usually stack additively: each source contributes a flat percentage, and the game adds them together into one total.

A character starting at 15% base crit chance who equips a weapon granting 10% and a talent granting 8% ends up with a total crit chance of 33%, found by simple addition: 15 + 10 + 8 = 33.

Crit damage bonuses from the same category also tend to add together first, forming one combined multiplier. A base crit multiplier of 1.5x (that is, +50% crit damage), plus 30% from gear, plus 20% from a passive skill, sums to +100% total crit damage, which converts to a 2.0x multiplier: 1 + (0.50 + 0.30 + 0.20) = 2.0.

Multiplicative stacking shows up when two bonuses come from separate, unrelated systems rather than the same additive bucket. A skill granting +20% crit damage (a 1.2x factor) combined with a fully separate modifier such as +15% damage under a specific condition (a 1.15x factor) multiplies rather than adds: 1.2 x 1.15 = 1.38, a 38% total increase. Simple addition would have predicted only 35%, so the multiplicative combo edges out the naive sum.

The practical rule: bonuses that modify the exact same stat, phrased the same way, almost always add together first. Bonuses coming from different systems, especially conditional ones tied to enemy health, positioning, or a separate skill tree, tend to multiply against the combined result instead.

What Does a Full Worked Example Look Like?

A complete example ties crit chance, crit damage, and stacking together into one calculation. Consider a character with 80 base damage per hit.

Crit chance comes from three additive sources: 15% base, 10% from a weapon, and 8% from a talent, totaling 33% (0.33). Crit damage comes from three additive sources feeding one multiplier: a 1.5x base crit multiplier (+50%), plus 30% from gear, plus 20% from a passive, totaling +100%, which converts to a 2.0x multiplier.

Plugging both totals into the formula: expected damage = 80 x (1 + 0.33 x (2.0 – 1)) = 80 x (1 + 0.33) = 80 x 1.33 = 106.4.

Adding one multiplicative modifier on top shows how a separate bucket changes the result further. A conditional effect granting +25% damage against low-health enemies (a 1.25x factor) applies after the crit math: 106.4 x 1.25 = 133.0 expected damage against a qualifying target. The crit chance and crit damage numbers stayed additive within their own categories, while the conditional bonus multiplied the final total.

Notice the expected-damage multiplier climbs in a straight line as crit chance rises, since the formula is linear in crit chance for a fixed multiplier. A higher crit multiplier steepens that line without changing its straight shape.

Should You Prioritize Crit Chance or Crit Damage?

Neither stat wins automatically; the better pick depends on how close crit chance already sits to 100%. Early on, crit chance usually delivers more expected damage per point invested, because a build with low crit chance leaves most attacks earning zero crit bonus at all.

Crit damage overtakes crit chance in value once crit chance sits close to its cap. A build already at 90% crit chance gains only 10 more percentage points of upside from chasing full 100%, while every point of crit damage keeps paying off on nearly every attack that already crits.

A useful mental shortcut: crit chance decides how often the bonus fires, and crit damage decides how big that bonus is. Low crit chance means crit damage upgrades go to waste most of the time, since the bonus rarely triggers. High crit chance means crit damage upgrades pay off on almost every attack, making them the stronger late-game investment.

Some builds deliberately chase 100% crit chance first specifically to make every point of crit damage fully reliable afterward. That order, chance first, then damage, tends to produce more consistent output than the reverse.

How Does Crit Math Differ Across RPGs, MOBAs, and Tabletop Games?

The underlying formula stays identical across genres, but the presentation and the number of rolls involved change. RPGs and MOBAs typically resolve crit chance behind the scenes on every single attack, often dozens of times per fight, which smooths results toward the expected-damage average quickly.

Tabletop wargames resolve far fewer rolls per game, often a handful of dice per unit per turn, so short-term results swing much further from the expected-damage average than in a video game. A tabletop crit chance of 33% can still miss every crit across an entire five-turn game purely from bad luck, even though the underlying math matches an RPG exactly.

Tabletop combat also frequently chains multiple probability steps together: a roll to hit, a separate roll to wound or penetrate armor, and only then a damage roll that a crit might double. The 40K Visual Dice Calculator is built around exactly this kind of layered tabletop probability, covering to-hit, to-wound, and save chances for Warhammer 40K combat. The same expected-value and stacking logic used here to model crit chance and crit damage drives every one of those tabletop probability steps, since both are just weighted averages over dice or attack rolls.

MOBAs add another wrinkle: crit effects sometimes trigger secondary effects, such as bonus armor penetration or a knockback, only on the critical hit itself. Those secondary effects need their own expected-value calculation layered on top of the base crit-damage formula, following the same additive-versus-multiplicative stacking rules already covered above.

What Are Common Mistakes When Reading Crit Stats?

Confusing crit damage bonus percentage with the full multiplier causes the most frequent errors. A stat sheet reading “+80% crit damage” means a 1.8x multiplier, not a straight 80% of base damage; the base damage still counts fully, plus 80% more.

Treating every crit-related bonus as additive causes a second common mistake. Conditional or cross-system bonuses frequently multiply instead, and assuming addition under-forecasts real damage output, sometimes by a meaningful margin as shown in the multiplicative stacking example above.

Ignoring the crit chance cap causes a third mistake. Crit chance cannot exceed 100% in nearly every game, so points invested past that ceiling produce zero additional expected damage and would have been better spent on crit multiplier or another stat entirely.

Comparing two builds by crit chance or crit damage alone, rather than by full expected damage, rounds out the common errors. A build with lower crit chance but a much higher crit multiplier can beat a high-crit-chance build with a modest multiplier, and only the full formula reveals which one actually deals more damage over time.

FAQs About Crit Chance and Crit Damage

Sources

This article is for general gaming and math education only, not a guarantee of any specific game’s exact mechanics, since implementations vary by title. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated September 18, 2026.