Critical chance and Critical Damage

Mechanic reference

Critical mechanics

6 minute read

See whether an attack can critical, how often it will critical against the selected resistance, and exactly how much damage the ordinary critical branch adds.

By RO Codex Team Updated August 7, 2026 Foundational mechanic · Reviewed August 7, 2026

How this damage is calculated

Calculation order

Eligibility and force/forbid state → clamp(CRI − target Critical Resistance + chance modifiers, 0, 100)% → clamp(150% + Critical Damage − target Critical Damage Reduction + damage modifiers, 100%, 10,000%) → family critical branch → event damage

Follow this order with your own build, but use the grouping and special branches shown by your skill family. The numerical example below demonstrates the mechanic rather than claiming one universal formula for every skill.

Build calculator

Enter your CRI, the target’s Critical Resistance, and both sides’ critical-damage modifiers. Results update as you type and show the proc chance, normal damage, critical damage, extra damage, average cast, and every independent-event outcome.

Instant result

Ordinary eligible criticals only

This calculator uses the client’s ordinary CRI-versus-resistance roll and 150% base critical scale. A forced, forbidden, magic, shared-roll, or physical rewritten critical must use that skill family’s exact rule.

Damage event

Use the non-critical result and independently rolled event count.

Normal event damage

The eligible event’s non-critical damage from its own skill-family calculation.

Independent damage events per cast

Use only when each event makes its own critical roll.

events

Critical chance

CRI − target resistance + applicable chance points, clamped from 0% to 100%.

CRI

Your final CRI after build and active effects.

Target Critical Resistance

Use the target’s effective total for this encounter state.

Other critical chance modifiers

Skill, card, race, HP, buff, or other modifiers that apply to this event.

Critical damage

150% base + Critical Damage − target reduction + applicable damage points.

Critical Damage

Added to the ordinary 150% base as percentage points.

Target Critical Damage Reduction

Subtracted from the critical scale as percentage points.

Other critical damage modifiers

Additional skill, buff, or branch terms that apply to this event.

Your calculated result

Against 91 Critical Resistance, 130 CRI gives this eligible attack a 39% critical chance. A critical deals 27,600 instead of 12,000 (+15,600), and two independent events average 36,168 damage per cast.

This calculator follows the ordering described on this page. Skill-specific rewrites and unsupported build lanes still require their own verified family support.

Example calculation: 130 CRI against Epic Sea

Worked example

This ordinary eligible critical example uses the captured Epic Sea profile’s 91 effective Critical Resistance. The attack deals 12,000 when it does not critical, the build has 130 CRI and +80% Critical Damage, and the target has no captured Critical Damage Reduction.

Use your own values

Replace the sample inputs with your character stats, selected skill level, active modifiers, and actual target. The values below are not a recommended build, damage target, or expected result for your character.

Normal event damage: 12,000
CRI: 130 chance points
Epic Sea Critical Resistance: 91 chance points
Other critical chance modifiers: 0 points
Base critical damage: 150% (×1.50)
Critical Damage: +80 percentage points
Target Critical Damage Reduction: 0 percentage points
Events per cast: 2 independent events

1
Effective critical chance clamp(130 − 91 + 0, 0, 100)
39%
2
Ordinary critical multiplier clamp(150% + 80% − 0% + 0%, 100%, 10,000%)
230% (×2.30)
3
Critical event damage 12,000 × 2.30
27,600
4
Extra damage when critical 27,600 − 12,000
+15,600
5
Normal contribution to average 12,000 × 61%
7,320
6
Critical contribution to average 27,600 × 39%
10,764
7
Average per eligible event 7,320 + 10,764
18,084
8
Average per two-event cast 18,084 × 2
36,168
9
No critical events 61%²
37.21% chance · 24,000 damage
10
Exactly one critical event 2 × 39% × 61%
47.58% chance · 39,600 damage
11
Two critical events 39%²
15.21% chance · 55,200 damage

Example result

Use the calculator above for the ordinary scaled-critical branch. A forced critical, forbidden critical, shared roll, magic-critical rule, or physical critical rewrite must use the selected skill family’s exact rule.

First ask whether the attack can critical

Critical chance is never the first check. The client rejects ineligible attack and roll types, honors effects that forbid criticals, and can force a critical before an ordinary roll is made. A skill, rune, card, status, stack, target state, or equipment effect can change that answer.

Magic criticals and some skill-specific criticals have additional eligibility and scaling branches. Do not apply the ordinary physical rule merely because the damage number is capable of showing a critical marker.

Eligible and rolled: calculate the effective chance.
Forced: the event enters its declared critical branch without using the ordinary chance.
Forbidden or ineligible: CRI and Critical Damage do nothing for that event.

How critical chance is calculated

For an ordinary eligible attack, start with your final CRI, subtract the target’s final Critical Resistance, add only the conditional modifiers that apply to this event, and clamp the result from 0 through 100. The clamped result is the event’s critical chance as a percentage.

CRI and Critical Resistance are opposing chance points. If a target’s published profile already gives the effective total, do not subtract its base and encounter bonus again as separate values.

Apply this to your build

130 CRI − 91 Critical Resistance + 0 other modifiers = 39% effective critical chance. Raising CRI from 130 to 140 changes that event to 49%, not 140%.

How much damage a critical deals

The ordinary physical critical scale starts at 150%. Add the attacker’s Critical Damage, subtract the target’s Critical Damage Reduction, add applicable conditional terms, then clamp the scale from 100% through 10,000%. Multiply the damage value owned by that family’s critical stage by this final scale.

Critical Damage is added to the 150% base as percentage points. With +80% Critical Damage and no reduction, the result is 230% (×2.30), not 150% × 180% (×2.70). Extra critical damage is simply critical event damage minus normal event damage.

Apply this to your build

A 12,000 ordinary event at 230% deals 27,600 when critical, which is 15,600 extra damage. Critical chance changes how often that result occurs; it does not change the 27,600 critical event itself.

Why some physical criticals need a different damage formula

An eligible ordinary physical attack can enter a critical rewrite that rebuilds damage from attack, size, element, race, MVP, reduction, refine, Vitality, and critical terms. That rewrite can bypass the ordinary Physical DEF calculation, so multiplying the final non-critical number by the critical scale would be wrong.

The calculator therefore shows the ordinary scaled-critical model and its independent-event outcomes. Use a verified skill-family article or Battle Lab ledger whenever the selected action declares a rewrite, a shared roll, a forced critical, or another specialized branch.

Apply this to your build

For a two-event skill, confirm whether each event rolls independently. Only then use the calculator’s zero-, one-, and two-critical outcome probabilities.

Evidence and freshness

RO Codex publishes Verified family articles only while the accepted handler and its required evidence remain current. Read the data quality standards for the site-wide accuracy contract.

Installed-client critical handlers: The extracted eligibility, critical-rate, and ordinary critical-scale handlers establish the calculation order, clamps, forced and forbidden states, and the physical critical rewrite warning.
Imported and captured combat properties: RO Codex keeps CRI, Critical Resistance, Critical Damage, and Critical Damage Reduction as separate player-facing properties. The example uses the captured Epic Sea profile’s effective 91 Critical Resistance.