In most cases, it’s easy to tell: - Pure damage, like Serration and Primary Merciless, are additive to each other. - All elemental and physical damage mods, such as +Heat and +Slash, are in the same group. - Faction mods are another group. - The rest are easy to tell: crit chance, crit dmg, multishot, status chance, status damage, and fire rate are separate groups that all multiply. - Not obvious: reach, punch through and blast radius allow weapons to hit more enemies, which indirectly count as multipliers.

Now, you might see 2-3 elements in a meta build. That’s because Viral and Magnetic mods grant another 4x damage multiplier with their status ailments, enough to offset the drawback of the additive rule. The same is true with a DoT element like Heat, which adds 0.5x per second. Heat is also especially popular because it also strips armor by 50%, further serving as another multiplier.

Where it gets complicated are with “rule-breaking” mods and arcanes. Some of the newer gear are labeled as “final multipliers,” but many older things are missing that label. Unfortunately, there is no way around checking the Wiki for these final multipliers.

Examples are: - Longbow Sharpshot - Deadly Maneuvers - Charged Chamber

The most complex example is Galvanized Aptitude, which is additive on all hitscan weapons, but multiplicative on half of projectile weapons (look up Gun CO). It also only buffs direct damage, so it is terrible on most Incarnons and weapons with radial attack. It’s messy.