FCR, FHR, and FBR have fixed breakpoint tables per class — you look up your value and you're done. IAS is different: your breakpoints depend on your class, weapon type, weapon WSM, and any skill-based speed buffs. The same 40% IAS gives completely different FPA on a Phase Blade vs a War Hammer. That's why an interactive calculator is essential.

Yes — IAS on the weapon absolutely counts. In D2R, the IAS that appears on your weapon (from its affix, a runeword like Fury or Passion, or socketed Shael runes / IAS jewels) is pooled together with your off-weapon IAS (gloves, charms, armor jewels), and the combined total is run through the diminishing-returns formula once: IEIAS = floor(120 × (weaponIAS + offWeaponIAS) / (120 + weaponIAS + offWeaponIAS)). Enter on-weapon IAS in the Weapon IAS% field and everything else in Off-Weapon IAS%. One caveat: when dual-wielding, only the IAS on the weapon you're currently swinging is used.

The formula IEIAS = floor(120 × IAS / (120 + IAS)) means each additional point of item IAS gives less EIAS than the last. Going from 0% to 40% IAS gives you 30 EIAS; going from 40% to 80% IAS gives you only 18 more. Skill buffs like Fanaticism bypass this and add directly — which is why they're so powerful.

Yes — SIAS sources are additive. An Assassin in a Fanaticism party gets both. At high levels (e.g., Lvl 20 BoS + Lvl 20 Fana = +60 + +40 = +100 SIAS), you'll often hit the EIAS cap of +75 with zero gear IAS, making additional IAS worthless.

Phase Blade has WSM −30 and is the fastest 1-handed sword. Chu-Ko-Nu crossbow has WSM −60. For Assassins, Runic Talons and Greater Talons have WSM −30. Lower (more negative) WSM means you reach fast breakpoints with less gear IAS.

Before patch 2.4, dual-clawing averaged both claws' WSM. After the patch, only the mainhand WSM applies. This calculator uses the post-2.4 behavior: mainhand WSM only. Select your mainhand claw in the weapon dropdown for accurate results.

For all dual-wield builds, only the primary (mainhand) weapon's IAS counts — offhand weapon IAS is ignored entirely. Enter only your mainhand weapon's IAS in the Weapon IAS% field.

For Barbarian and Assassin, an Offhand Weapon selector appears — pick your second weapon and the calculator handles the WSM correctly per class. Barbarian dual-wield (Frenzy, Double Swing) averages the two weapons' WSM, floored: WSM = floor((mainhand + offhand) / 2) — so a fast mainhand + slow high-damage offhand reads at the true averaged speed, not the mainhand's. Assassin dual-claw uses mainhand WSM only (post-2.4), so the offhand claw's WSM doesn't change your speed. In both cases the offhand's IAS is ignored — only the mainhand weapon's IAS (entered in Weapon IAS%) counts.

The Warlock class (added with Reign of the Warlock / Season 13) uses Necromancer animation data for attack animations. This calculator applies those animation values for Warlock. The Warlock can use standard weapons (not claws) and benefits from Fanaticism like any other class.

Patch 3.2 (May 22, 2026): The attack-speed bonus from Warlock's skill is now capped at +50%. Stacking +AS beyond 50% from skill investment yields no additional benefit — gear IAS continues to apply normally on top of the capped skill bonus.

EIAS is capped at +75 for human form and +150 for wereforms (Werewolf/Werebear). It also has a minimum of −85. Any EIAS calculated outside these bounds is clamped to the limit.

Whirlwind in D2R uses a special formula and doesn't follow standard attack animation rules. The calculator shows the base FPA for Barbarian standard attack with your weapon, which is a useful reference, but WW has its own mechanics. For dedicated WW builds, community resources at Amazon Basin or Phrozen Keep have WW-specific tables.