What's the minimum crit chance I should aim for in D4?

Stack crit chance until p_breakeven = 100 × (csd_mult − 2) / (csd_mult − 1). With default 250% CSD that's ~33%; with 350% CSD it's 60%; with 500%+ it's 75%+. Below this threshold, every +1% crit chance is worth more than +1% additive damage; above it, additive starts winning.

How does CSD interact with crit chance?

Multiplicatively. Effective crit damage on a hit = base × (1 + crit_chance × (csd_mult − 1)). Higher CSD makes each crit more valuable, which raises the breakeven crit chance — at higher CSD you should keep stacking crit longer before switching to additive.

Does this apply to Vulnerable / Overpower / Berserk too?

Partially. Those are separate multiplicative buckets that compound on top of the base × additive × crit math. The breakeven derivation here is for crit-vs-additive specifically. Full multi-bucket analysis (csd vs vulnerable, vulnerable vs overpower, etc.) is upcoming as the engine grows ARPG coverage.

Why doesn't this cover armor / EHP / lucky hit?

The engine currently models flat damage reduction and percentage resistance, not the D4 armor curve (DR = armor / (armor + 5 × monster_level + 850)) or lucky hit proc gates. Those defensive and proc-gating questions are tracked in the manual-triage queue for the next ARPG engine increment.

Concepts → D4 crit chance breakeven

Published 4 May 2026

Diablo 4 — when does `+1% crit chance` beat `+1% additive damage`?

The "minimum crit chance to aim for" question has a closed form. The answer depends entirely on your Critical Strike Damage stat. Below ~33% crit chance with default (250%) CSD, every +1% crit chance beats +1% additive. Above the breakeven, additive starts winning.

The damage formula

D4 hits always land (no to-hit roll). Damage on a single attack:

damage = base × (1 + additive%/100) × (1 + crit_chance%/100 × (csd_mult − 1))

Where csd_mult is the total crit multiplier — 1.5 for a baseline (no CSD stat) crit, 2.5 for a +100% CSD stat, 3.5 for a +200% CSD stat, etc. The two terms are independent multipliers: additive damage scales the base, crit chance + CSD scale the expected per-hit value.

The marginal-value comparison

The marginal value of +1 percentage point of crit chance, holding additive damage at 0:

∂damage/∂(crit_chance) = base × (csd_mult − 1) / 100

The marginal value of +1 percentage point of additive damage, holding crit chance at p%:

∂damage/∂(additive) = base × (1 + p/100 × (csd_mult − 1)) / 100

Set them equal — that's the crit chance at which +1% crit and +1% additive contribute the same DPS:

p_breakeven = 100 × (csd_mult − 2) / (csd_mult − 1)

Below p_breakeven, every +1% crit chance is worth more than +1% additive damage. Above it, additive starts winning.

The breakeven table

Read this as "I should stack crit chance until I hit roughly this percentage, then additive damage takes over."

CSD stat	`csd_mult`	`p_breakeven`	Practical read
+0% (base)	1.5×	—	Additive always wins. CSD is too low for crit chance to compete.
+50%	2.0×	0%	Borderline. Crit and additive are equivalent at the very start; additive wins thereafter.
+100%	2.5×	~33%	Stack crit until 33%, then additive. Default endgame target.
+200%	3.5×	60%	Stack crit until 60%. High-CSD builds (Vulnerable + crit-stacking gear) live here.
+400%	5.5×	~78%	Stack crit aggressively. Late endgame with Tempering / Mythic Uniques pushing CSD.

Worked example — 100 base, 30% crit, 250% CSD

Live: /strike/100~hit100crit30csd250

With 30% crit chance and 250% CSD, you're slightly under the ~33% breakeven. Crit chance is still slightly more valuable than additive damage at this point.

Hit branch (70%): 100 damage
Crit branch (30%): 250 damage
Expected per attack: 0.7 × 100 + 0.3 × 250 = 145

Compare to /strike/100~hit100crit30csd350 (350% CSD): expected 175 — the same 30% crit chance produces ~21% more damage when CSD is higher, AND the crit-vs-additive breakeven shifts up to 60%, so you should keep stacking crit longer.

What this answers (and what it doesn't)

Answers: the marginal-value question between two stat buckets — should you take +1% crit chance or +1% additive damage on a given affix slot?

Doesn't answer:

Multi-bucket multiplicative damage: D4 has Vulnerable, Overpower, Berserk, and several weapon/skill multipliers in separate buckets. The full formula compounds these multiplicatively. The csd vs additive breakeven shown here is a 2-bucket simplification; full builds need to compare against ALL active multipliers.
Lucky Hit chance: gates secondary-effect procs (chill, poison, freeze). Engine doesn't model lucky-hit gates yet. Surface in the inbound monitor as manual-triage.
Armor mitigation curve: DR = armor / (armor + 5 × monster_level + 850) with diminishing returns. Engine has flat dr<n> but not the diminishing-returns curve.
Effective HP / defensive math: comparing two builds' tankiness needs the full mitigation pipeline (resist × armor × block × dodge). Same engine gap as armor.
Tooltip DPS vs effective DPS: tooltips show per-hit damage; real DPS depends on attack speed × uptime × proc rates. Separate concept worth its own pillar.

For now: this pillar covers the cleanest possible D4 build decision (crit-vs-additive on a single affix slot). Multi-bucket stacking, Lucky Hit, armor, and EHP are upcoming as the engine grows ARPG coverage.