OA and DA Explained

How Probability To Hit (PTH) Works

Every attack computes a Probability To Hit from the attacker's OA and the defender's DA.

• ▸The PTH formula (Japanese Wiki's simplified form, mathematically equivalent to the official guide's): PTH = 315 x OA / (DA + 3.5 x OA) + 0.02275 x (OA - DA) + 20.
• ▸PTH has a floor of 55 - no matter how low your OA, you still connect at the 55% level.
• ▸Below 70 PTH attacks graze: damage is multiplied by PTH/70 (about 78.6% of normal at the 55 floor).
• ▸At 90 PTH and above critical hits start occurring, with the multiplier tier rising alongside PTH up to the x1.5 maximum at 135+ (see the official guide's table for the exact tiers).
• ▸Avoidance checks - dodge, fumble, projectile deflection - are resolved before the OA-versus-DA roll.

What OA (Offensive Ability) Determines

• ▸OA feeds everything offensive in the roll: hit chance, crit chance, and the crit-multiplier tier. Think of it as the stat that makes your damage reliable.
• ▸Main sources: Cunning, gear and affixes, skills (passives/buffs), and devotion.
• ▸Debuffs that reduce enemy DA improve your hits and crits in the same direction as extra OA (the PTH formula is asymmetric in OA and DA, so equal numbers are not strictly equivalent).
• ▸How much OA you need depends on the enemy's DA - there is no universal target. Follow the recommendation on each build page for your content and crit reliance.

What DA (Defensive Ability) Determines

• ▸DA lowers the PTH enemies roll against you - reducing both how often you get hit and how often you get crit.
• ▸Insufficient DA means frequent enemy crits (up to x1.5), causing sudden deaths even with capped resistances.
• ▸Main sources: Physique, gear and affixes, skills, and devotion.
• ▸During the campaign DA rarely falls short (per the Japanese Wiki); it mostly becomes a problem in Ultimate endgame content.

How to Treat Target Numbers

• ▸OA and DA only mean something relative to the enemy's numbers - no single value is correct everywhere.
• ▸The Japanese Wiki states that highest-difficulty endgame content with AoM onward often demands roughly 2800-3000 DA, and this article adopts that as its guideline.
• ▸That guideline is aimed at Shattered Realm / Crucible-grade content; clearing the campaign needs far less.
• ▸We give no flat OA target because it varies with a build's crit reliance - defer to each build page's recommendation.

1. Official Grim Dawn Game Guide: Combat — Confirms OA/DA governing hits and crits, the official PTH formula, the x1.5 maximum crit multiplier, and avoidance checks resolving before the OA-vs-DA roll.
2. Grim Dawn Japanese Wiki: Combat Mechanics — Confirms the simplified PTH formula, the 55 floor, sub-70 grazes (damage x PTH/70, ~78.6% at the floor), and the Japanese stat names (the crit-onset boundary of 90 PTH inclusive follows the official guide's table).
3. Grim Dawn Japanese Wiki: Survivability Advice — Confirms the guideline that highest-difficulty endgame with AoM onward often demands roughly 2800-3000 DA, and that DA rarely falls short during the campaign.
4. Official Crate Forum: Grim Dawn v1.2.1.6 + Hotfix — Official patch notes for the verified version.