Attack Speed

The frequency with which units attack is measured in Attack Speed. A unit's attack speed can be modified by items, Agility, abilities, and auras. The minimum attack speed is 20, or every 8.50 seconds.

Base attack time
Every unit has a base attack time (BAT). It is the interval in seconds between each attack. This base value generally cannot change (except by certain Hero transformation abilities, such as Alchemist's Chemical Rage), but what can change is the unit's increased attack speed.

All Heroes have a BAT of 1.7 except for the following:

Increased attack speed
Increased attack speed (IAS) gives you a percentage of your base attack speed (or attack per second). Each point in Agility increases IAS by 1, and items and abilities can affect it as well. It works together with base attack time to determine how often a unit can attack. As it is a percentage bonus, attack speed increases linearly, and doubles at 100 IAS, maxing out at 400 (attack speed divided by 5). IAS cannot fall below the value of -80 (attack speed multiplied by 5).


 * Note: When mousing over attack damage in the HUD, the first field shows the Attack Speed and the time per attack in parenthesis. This Attack Speed field is defaulted to 100 and adds the IAS, so the lowest is can go is 20 and is maxed at 500. The value can be displayed as outside the range of these values however, but the time per attack correctly displays these limits. This value also seems to be adjusted for heroes without 1.7 BAT.

Attack speed formula
To determine how often a unit attacks, the formula below is used:


 * Attack Time = BAT / (1 + IAS)
 * Attacks per Second = (1 + IAS) / BAT

IAS is a percentage, so you must divide your actual IAS by 100 before using it in this formula. IAS reduces a percentage of your BAT, thus giving you a corresponding percentage of attack per second as follow: +1 IAS equals +1% of your attack speed.

For example: +100 IAS = +100% attack per second, meaning your attack speed doubles or BAT reduced by half.

List of Items that give Increased Attack Speed
* Item provides increased attack speed exclusively via Agility.

List of Items and Abilities that reduce Increased Attack Speed
* Affects allied heroes.
 * }

** Affected units' attack speed to 100

*** Affects self.