Attack Speed (often shortened as AS or ASPD) is the frequency of a champion's basic attacks. They are measured and displayed as attacks per second.
 Attack speed cannot be increased beyond 2.5 attacks per second (or 1 attack every two fifths of a second, or 0.4 seconds).
Attack speed bonuses (from items or abilities, etc.) are in percent. The bonus is a percentage of the champions base attack speed. Therefore, champions with higher base attack speed benefit more from attack speed increases. Like all stats, one's attack speed can be increased via leveling up, items, runes, masteries, buffs, and abilities. Some items and abilities (only those two) decrease enemy attack speed.
Calculations
Base attack speed
Every champion's base attack speed (AS_{base}) is calculated using a hidden variable called attack delay,^{[1]} which ranges from −0.10 to 0.3. (AS_{base}) is the total number shown at level 1 without runes, masteries, etc. It is represented this way throughout the wiki.
Bonus attack speed sources
 Champions gain an attack speed percentage every time they level up, which ranges from roughly 0  6% (the exact number depending on the specific champion) and can be calculated through the statistics growth formula.
 Items
 Champion abilities
 Masteries
 Attack Speed runes
Bonus AS% stacks additively.
 Example: grants +35% attack speed and also grants +50% attack speed, so the champion gains +85% in total.
Notes:
 Final attack speed cannot go above the cap of 2.5 attacks per second.
 Many ingame tooltip percentages (such as runes) have been rounded, so results may be slightly different unless the precise numbers are known.
Example
 Calculating base attack speed:
 attack delay is −0.04.
 . This is base attack speed, seen at level 1 (without runes, masteries, etc.).
 The number seen in game is rounded to 3 decimal places: 0.651.
 Calculating "bonus attack speed":
 Every time statistics growth formula.
 At level 18 he has gained as bonus AS%.
levels up, he gains bonus AS% based on percentage growth 3.22% and his level through the  At 18 he has maxed increasing his attack speed by 30%.
 Let's say he has the mastery up to 4%.
 Let's also say he has : +35%.
 All together he has: 54.74% + 30% + 4% + 35% = 123.74% bonus AS% or 1.2374 bonus AS as a decimal.
 Every time statistics growth formula.
 Final calculation:
 In game, the number will be shown as: 1.457.
Increasing attack speed
Items
 Unique: Heals and shields on allied champions (excluding yourself) enhance their basic attacks for 6 seconds. Granting them +20%  35% (based on level) attack speed and 20  35 (based on level) bonus onhit magic damage healing them for the same amount. : Passive:
 +8% attack speed, +3 attack damage and +4 ability power for 5 seconds, stacking up to 6 times, granting a total of +48% attack speed, +18 attack damage and +24 ability power. At 6 stacks, gain Guinsoo's Rage. : +25% attack speed. Passive: Basic attacks grant
Champion abilities
Note: Only the attack speed buff effect of these abilities is shown here, to read more information on each of these abilities, follow the link on each of them.
 attack speed by 0.6  1.1 (based on level)% for every 2% in the Blood Well.
 attack speed by 40 / 50 / 60% for 12 seconds. increases his
passively increases his  bonus attack speed by 20 / 25 / 30 / 35 / 40% for the next 4 seconds. grants her
 attack speed by 20 / 30 / 40 / 50 / 60%. passively increases his
 attack speed by 30 / 38 / 46 / 54 / 62% for 5 seconds. increases his
 20% bonus attack speed. passively grants her
 attack speed by 20 / 25 / 30 / 35 / 40% for 3 seconds. increases his
 attack speed of herself and her Spiderlings by 60 / 80 / 100 / 120 / 140% for 3 seconds. increases the
 attack speed by 60 / 75 / 90 / 105 / 120% for 3 seconds after attacking with . increases her
 attack speed by 10 / 12 / 14% whenever he hits a target with any of his abilities. This bonus lasts for 6 seconds and stacks up to 5 times, for a maximum of 50 / 60 / 70%.
 attack speed of allied champions it passes through by 20 / 25 / 30 / 35 / 40% for 5 seconds. increases the
passively increases his  attack speed by 50% for her 2 next basic attacks. increases her
 attack speed by 5.5  99 (based on level)% when in .
 bonus attack speed by 20 / 30 / 40 / 50 / 60% for 3 seconds. grants him
passively increases his  attack speed by 15 / 17.5 / 20 / 22.5 / 25%. When activated, it throws a flag that increases nearby allied champions and his own attack speed by the same amount. passively increases his
 attack speed by 3.5  11 (based on level)%. This bonus lasts for 2.5 seconds and stacks up to 8 times, for a maximum of 28  88 (based on level)%, falling off one stack at a time every 0.25 seconds. causes his basic attacks to increase his
 attack speed to 2.5 for the next three basic attacks. increases his
 15% total attack speed for 6 seconds whenever an enemy champion or structure dies within 3 seconds of being damaged by her, stacking indefinitely.
 0  70 (based on level)% plus 30 / 40 / 50 / 60 / 70% attack speed. causes her basic attacks to grant bonus attack speed for 2.5 seconds, stacking up to 3 times for a maximum of
grants her  150% bonus attack speed on his next 4 attacks within 4 seconds. grants him
 attack speed by 15 / 20 / 25 / 30 / 35%. passively increases his
 attack speed by 40% of his next two 2 autoattacks within the next 3 seconds after casting an ability. increases the
 25 / 30 / 35 / 40 / 45% bonus attack speed for the next 3 / 3.25 / 3.5 / 3.75 / 4 seconds. grants target ally champion
 attack speed by 30 / 55 / 80% for 7 seconds. Kills and assists extends the duration by 7 seconds. increases his
 attack speed by 40 / 55 / 70 / 85 / 100% for 6 seconds. increases her
 attack speed by 20 / 30 / 40 / 50 / 60% for 7 seconds. increases allied target's
 20 / 25 / 30 / 35 / 40% attack speed. Upon activation, it summons a spell shield for 1.5 seconds, if the shield successfully blocks a spell, the attack speed bonus is doubled to 40 / 50 / 60 / 70 / 80% attack speed for 5 seconds. passively grants himself
 attack speed by 25 / 30 / 35 / 40 / 45% for 12 seconds. increases an allied unit's and his own
 attack speed by 1% per 1% health he is missing.
 attack speed by 40 / 50 / 60 / 70 / 80% for 6 seconds. increases his
passively increases his  attack speed by 20 / 25 / 30 / 35 / 40% for 3 seconds when she attacks a target marked by . increases her
 20 / 40 / 60% bonus attack speed. passively grants her
 50% bonus attack speed on his next 3 autoattacks within the next 8 seconds if his Spirit Blade collides with an enemy champion. grants him
 30 / 45 / 60% attack speed while is active. passively grants her
 100% total attack speed for his next 2 autoattacks within 4 seconds after casting an ability. grants him
 attack speed by 20 / 40 / 60 / 80% for 3 seconds after leaving his stealth state. increases his
 attack speed by 30 / 50 / 70 / 90 / 110% for 5 seconds. increases her
 attack speed by 20 / 35 / 50 / 65 / 80%. coats the target location with ice for 8 seconds. While on this area, Trundle increases his
 attack speed by 10 / 15 / 20 / 25 / 30%. passively increases his
 attack speed by 30 / 35 / 40 / 45 / 50% for up to 5 seconds after revealing himself. increases his
 attack speed by 10% upon switching stances. This bonus lasts for 5 seconds and stacks up to 3 times, for a maximum of 30%.
 attack speed by 30 / 40 / 50 / 60 / 70% for 5 seconds on activation. increases his
increases his  attack speed by 20% for 3 seconds on minion kills, while a champion kill/assist will grant 40% for 6 seconds. increases
 attack speed by 30 / 35 / 40 / 45 / 50% for 4 seconds after attacking the same target 3 times. will increase her
 attack speed by 4 / 8 / 12 / 16 / 20%. This bonus stacks up to 3 times, for a maximum of 12 / 24 / 36 / 48 / 60%, and lasts for 4 seconds. passively causes his auto attacks to increase his
 attack speed by 40 / 50 / 60 / 70 / 80% and half of that amount to nearby allied champions for 6 seconds. increases his
 attack speed by 30 / 35 / 40 / 45 / 50% after hitting a target with this skill. increases his
 attack speed by 40 / 50 / 60 / 70 / 80% for 5 seconds. increases his
Masteries
 : Increases champion attack speed by 0.8 / 1.6 / 2.4 / 3.2 / 4%.
Runes
Reducing attack speed
Note: Attack speed reductions stack multiplicatively and take percentages off the final attack speed value after all bonus attack speed has been factored in.
Items
 Unique: Cripples nearby enemies' attack speed by 15% (700 range). : Aura:
 Unique: 20% critical strike damage taken from basic attacks. : Passive:
 Unique – Cold Steel: When hit by basic attacks, cripples source's attack speed by 15% for 1 second. : Passive:
Summoner Spells
 : Active: Exhausts target enemy champion, reducing their movement speed and their damage dealt by 40% for 2.5 seconds.
Champion abilities
Note: Only the attack speed reduction effect of these abilities is shown here, to read more information on each of these abilities, follow the link on each of them.
 slows affected enemy champion's attack speed by 50% for 1.5 seconds.
 slows affected units' attack speed by 30 / 35 / 40 / 45 / 50% for 3 seconds.
 reduces an enemy unit's attack speed by 17.5% plus an additional 1.5 / 3 / 4.5 / 6 / 7.5% per second for 5 seconds, for a total of 23.5 / 29.5 / 35.5 / 41.5 / 47.5%.
 reduces an enemy unit's attack speed by 25% for 3 seconds.
 slows the attack speed of all nearby enemy units by 25% while channeling for 3 seconds.
Notes
 All percentages listed in a champion's attack speed statistic are approximations.
 Attack speed reductions are affected by crowd control reduction and Slow Resist.
cooldown reduction per attack with ).
List of champions' attack speed
Champion Level  Top 5 champions  Bottom 5 champions  

Level 1  1.  0.694 AS  1.  0.481 AS  
1.  
1.  
1.  
1.  
2.  0.69 AS  2.  0.568 AS  
2.  
3.  0.679 AS  3.  0.571 AS  
3.  
3.  
3.  
3.  
3.  
4.  0.672 AS  4.  0.579 AS  
4.  
5.  0.67 AS  5.  0.601 AS  
5.  
5.  
5.  
Level 18  1.  1.105 AS  1.  0.678 AS  
2.  1.089 AS  2.  0.712 AS  
3.  1.087 AS  3.  0.717 AS  
4.  1.07 AS  4.  0.731 AS  
5.  1.06 AS  5.  0.731 AS  
5.  
5. 
Trivia
Last updated: October 11, 2016 – V6.20
 The most attack speed a champion can reach at level 1 with the initial 500 is 2.50 with .
 Base AS: 0.625 AS
 Bonus AS: +147.4% AS
 Buffs: +90% AS
 (+25% AS)
 (+25% AS)
 (+20% AS)
 (+20% AS)
 Runes: +41.4% AS
 9 × Marks of Attack Speed (+9 × 1.7% AS)
 9 × Seals of Attack Speed (+9 × 0.76% AS)
 9 × Glyphs of Attack Speed (+9 × 0.64% AS)
 3 × Quintessences of Attack Speed (+3 × 4.5% AS)
 Item: +12% AS
 One (+12% AS)
 Masteries: +4% AS
 5 points in (+4% AS)
 AS Amplification: +100% total AS
 (+100% total AS)
 Buffs: +90% AS
 Relevant mathematics:
Champion statistics  

Offensive 

Defensive  
Magical  
Movement 