Flat damage

Flat damage refers to stats that add base damage. Base damage is calculated first. For more info about the entire damage calculation process see Receiving damage.

Identifying Flat Damage
All flat damage modifiers have a base stat number and damage type.

Some modifiers apply limitations to the damage source.

If there is no limitation this implies a Global modifier, which is sometimes called a generic modifier.

Some modifiers have variable stats and others have 1 stat.

Flat damage comes in 2 forms. Minimum damage damage and maximum damage.

Anything that says is considering minimum damage. Minimum damage will always apply to every hit.

Anything that says is adding a minimum and maximum damage range. The maximum damage represent the maximum range of damage possible.

Damage Types
Flat damage can come in all of the 5 damage types. See each page for more examples of each flat damage source.
 * Physical damage
 * Lightning damage
 * Fire damage
 * Cold damage
 * Chaos damage

Limitations
Flat damage is capable of affecting all hits, including those applied by attacks, spells, minions and secondary damage. It does not affect damage over time from any source, including minions.

Global damage will apply to all hits, except for minions which scale their own damage. Affects that only apply to one source (like minions) explicitly state so in the modifier. There is no specific flat damage that only applies to secondary damage, but global damage will apply to secondary damage.

Damage Scaling
Average damage - To calculate your average flat damage add up your minimum and maximum damage and divide them by 2. To calculate flat added attack damage, take the average or minimum damage and divide that by your other total flat sources total average or minimum and the answer is the amount of more damage that one source gave you.

Spell damage is the same calculations above, except non spell sources are multiplied by the damage multiplier on the spell gem. These calculations are different because the damage on the gem itself is not multiplied by the damage multiplier, which is different than attacks.

Secondary damage has the same calculations as spell damage. For example Herald of Ice.

Support gems - Flat damage from support gems can potentially do more or less damage than other options available. It is also possible for them to give the most damage at one point and not so at another. Non-gem sources that affect your flat damage and the level of the support gem can change the total damage granted by flat damage.
 * Combos - Innervate support can add flat damage without being linked to the main skill used for damage.
 * Support gem level - Flat added damage values from gems benefit more from plus gem levels than % more damage support gems. Especially at higher levels. (There may be exceptions to this)
 * Example - A spellcaster with lightning damage has elemental focus and added lightning damage support with plus 7 levels to support gems. Elemental focus goes from 49 to 56% more damage from level 20 to 27. 7 / 49 = 14.2% more damage than the gem added before (not 14.2% more damage total). Added lightning damage adds around double the previous flat added lightning damage from level 20 to 27, therefore it gives 100% more damage than the gem added before.