Attack delay, also known as attack speed offset, is the hidden variable that is used to calculate a champion's "base attack speed." The formula for this calculation is as follows:

\pagecolor{Black}\color{White}{\it AS}_{\rm base}={0.625 \over 1+{\it attack\ delay}}

A negative attack delay corresponds to a higher base attack speed (i.e. attacks per second), which consequently makes bonus attack speed more effective.

Contrary to popular believe, attack delay is not responsible for how "good" an attack feels. A number of other hidden variables are used to determine when an attack wind-up is considered complete as well as when an attack is considered to have hit - e.g. some projectile-based attackers can click to move the moment the projectile is airborne, whereas others may "cancel" the attack at any point prior to the projectile hitting. These variables is not viewable/accessible.

Champion Attack delay Calculated base attack speed
Decimal
(mouseover for expansion)
Precise
fraction
AatroxSquare Aatrox−0.040.6510.625 ÷ 0.96
AhriSquare Ahri−0.0650.6680.625 ÷ 0.935
AkaliSquare Akali−0.10.6940.625 ÷ 0.9
AlistarSquare Alistar00.6250.625 ÷ 1
AmumuSquare Amumu−0.020.6380.625 ÷ 0.98
AniviaSquare Anivia00.6250.625 ÷ 1
AnnieSquare Annie0.080.5790.625 ÷ 1.08
AsheSquare Ashe−0.050.6580.625 ÷ 0.95
Aurelion SolSquare Aurelion Sol00.6250.625 ÷ 1
AzirSquare Azir−0.020.6380.625 ÷ 0.98
BardSquare Bard00.6250.625 ÷ 1
BlitzcrankSquare Blitzcrank00.6250.625 ÷ 1
BrandSquare Brand00.6250.625 ÷ 1
BraumSquare Braum−0.030.6440.625 ÷ 0.97
CaitlynSquare Caitlyn0.10.5680.625 ÷ 1.1
CamilleSquare Camille00.6250.625 ÷ 1
CassiopeiaSquare Cassiopeia−0.0340.6470.625 ÷ 0.966
Cho'GathSquare Cho'Gath00.6250.625 ÷ 1
CorkiSquare Corki−0.020.6380.625 ÷ 0.98
DariusSquare Darius00.6250.625 ÷ 1
DianaSquare Diana00.6250.625 ÷ 1
Dr. MundoSquare Dr. Mundo00.6250.625 ÷ 1
DravenSquare Draven−0.080.6790.625 ÷ 0.92
EkkoSquare Ekko00.6250.625 ÷ 1
EliseSquare Elise00.6250.625 ÷ 1
EvelynnSquare Evelynn00.6250.625 ÷ 1
EzrealSquare Ezreal00.6250.625 ÷ 1
FiddlesticksSquare Fiddlesticks00.6250.625 ÷ 1
FioraSquare Fiora00.6250.625 ÷ 1
FizzSquare Fizz−0.050.6580.625 ÷ 0.95
GalioSquare Galio00.6250.625 ÷ 1
GangplankSquare Gangplank00.6250.625 ÷ 1
GarenSquare Garen00.6250.625 ÷ 1
GnarSquare Gnar00.6250.625 ÷ 1
GragasSquare Gragas00.6250.625 ÷ 1
GravesSquare Graves0.30.4810.625 ÷ 1.3
HecarimSquare Hecarim−0.06720.670.625 ÷ 0.9328
HeimerdingerSquare Heimerdinger00.6250.625 ÷ 1
IllaoiSquare Illaoi00.6250.625 ÷ 1
IreliaSquare Irelia−0.060.6650.625 ÷ 0.94
IvernSquare Ivern−0.030.6440.625 ÷ 0.97
JannaSquare Janna00.6250.625 ÷ 1
Jarvan IVSquare Jarvan IV−0.050.6580.625 ÷ 0.95
JaxSquare Jax−0.020.6380.625 ÷ 0.98
JayceSquare Jayce−0.050.6580.625 ÷ 0.95
JhinSquare Jhin00.6250.625 ÷ 1
JinxSquare Jinx00.6250.625 ÷ 1
KalistaSquare Kalista−0.030.6440.625 ÷ 0.97
KarmaSquare Karma00.6250.625 ÷ 1
KarthusSquare Karthus00.6250.625 ÷ 1
KassadinSquare Kassadin−0.0230.640.625 ÷ 0.977
KatarinaSquare Katarina−0.050.6580.625 ÷ 0.95
KayleSquare Kayle−0.020.6380.625 ÷ 0.98
KaynSquare Kayn00.6250.625 ÷ 1
KennenSquare Kennen−0.09470.690.625 ÷ 0.9053
Kha'ZixSquare Kha'Zix−0.0650.6680.625 ÷ 0.935
KindredSquare Kindred00.6250.625 ÷ 1
KledSquare Kled00.6250.625 ÷ 1
Kog'MawSquare Kog'Maw−0.060.6650.625 ÷ 0.94
LeBlancSquare LeBlanc00.6250.625 ÷ 1
Lee SinSquare Lee Sin−0.040.6510.625 ÷ 0.96
LeonaSquare Leona00.6250.625 ÷ 1
LissandraSquare Lissandra00.6250.625 ÷ 1
LucianSquare Lucian−0.020.6380.625 ÷ 0.98
LuluSquare Lulu00.6250.625 ÷ 1
LuxSquare Lux00.6250.625 ÷ 1
MalphiteSquare Malphite−0.020.6380.625 ÷ 0.98
MalzaharSquare Malzahar00.6250.625 ÷ 1
MaokaiSquare Maokai−0.10.6940.625 ÷ 0.9
Master YiSquare Master Yi−0.080.6790.625 ÷ 0.92
Miss FortuneSquare Miss Fortune−0.04730.6560.625 ÷ 0.9527
MordekaiserSquare Mordekaiser0.040.6010.625 ÷ 1.04
MorganaSquare Morgana00.6250.625 ÷ 1
NamiSquare Nami−0.030.6440.625 ÷ 0.97
NasusSquare Nasus−0.020.6380.625 ÷ 0.98
NautilusSquare Nautilus0.020.6130.625 ÷ 1.02
NidaleeSquare Nidalee−0.020.6380.625 ÷ 0.98
NocturneSquare Nocturne−0.0650.6680.625 ÷ 0.935
NunuSquare Nunu00.6250.625 ÷ 1
OlafSquare Olaf−0.10.6940.625 ÷ 0.9
OriannaSquare Orianna−0.050.6580.625 ÷ 0.95
OrnnSquare Ornn−0.080.6790.625 ÷ 0.92
PantheonSquare Pantheon−0.030.6440.625 ÷ 0.97
PoppySquare Poppy00.6250.625 ÷ 1
QuinnSquare Quinn−0.0650.6680.625 ÷ 0.935
RakanSquare Rakan00.6250.625 ÷ 1
RammusSquare Rammus00.6250.625 ÷ 1
Rek'SaiSquare Rek'Sai00.6250.625 ÷ 1
RenektonSquare Renekton−0.060.6650.625 ÷ 0.94
RengarSquare Rengar00.6250.625 ÷ 1
RivenSquare Riven00.6250.625 ÷ 1
RumbleSquare Rumble−0.030.6440.625 ÷ 0.97
RyzeSquare Ryze00.6250.625 ÷ 1
SejuaniSquare Sejuani00.6250.625 ÷ 1
ShacoSquare Shaco−0.10.6940.625 ÷ 0.9
ShenSquare Shen00.6250.625 ÷ 1
ShyvanaSquare Shyvana−0.050.6580.625 ÷ 0.95
SingedSquare Singed0.020.6130.625 ÷ 1.02
SionSquare Sion−0.080.6790.625 ÷ 0.92
SivirSquare Sivir00.6250.625 ÷ 1
SkarnerSquare Skarner00.6250.625 ÷ 1
SonaSquare Sona−0.030.6440.625 ÷ 0.97
SorakaSquare Soraka00.6250.625 ÷ 1
SwainSquare Swain00.6250.625 ÷ 1
SyndraSquare Syndra00.6250.625 ÷ 1
Tahm KenchSquare Tahm Kench00.6250.625 ÷ 1
TaliyahSquare Taliyah00.6250.625 ÷ 1
TalonSquare Talon−0.0650.6680.625 ÷ 0.935
TaricSquare Taric00.6250.625 ÷ 1
TeemoSquare Teemo−0.09470.690.625 ÷ 0.9053
ThreshSquare Thresh00.6250.625 ÷ 1
TristanaSquare Tristana−0.04730.6560.625 ÷ 0.9527
TrundleSquare Trundle−0.06720.670.625 ÷ 0.9328
TryndamereSquare Tryndamere−0.06720.670.625 ÷ 0.9328
Twisted FateSquare Twisted Fate−0.040.6510.625 ÷ 0.96
TwitchSquare Twitch−0.080.6790.625 ÷ 0.92
UdyrSquare Udyr−0.050.6580.625 ÷ 0.95
UrgotSquare Urgot0.050.5950.625 ÷ 1.05
VarusSquare Varus−0.050.6580.625 ÷ 0.95
VayneSquare Vayne−0.050.6580.625 ÷ 0.95
VeigarSquare Veigar00.6250.625 ÷ 1
Vel'KozSquare Vel'Koz00.6250.625 ÷ 1
ViSquare Vi00.6250.625 ÷ 1
ViktorSquare Viktor−0.050.6580.625 ÷ 0.95
VladimirSquare Vladimir−0.050.6580.625 ÷ 0.95
VolibearSquare Volibear−0.050.6580.625 ÷ 0.95
WarwickSquare Warwick−0.020.6380.625 ÷ 0.98
WukongSquare Wukong−0.050.6580.625 ÷ 0.95
XayahSquare Xayah00.6250.625 ÷ 1
XerathSquare Xerath00.6250.625 ÷ 1
Xin ZhaoSquare Xin Zhao00.6250.625 ÷ 1
YasuoSquare Yasuo−0.0670.670.625 ÷ 0.933
YorickSquare Yorick00.6250.625 ÷ 1
ZacSquare Zac−0.020.6380.625 ÷ 0.98
ZedSquare Zed−0.040.6510.625 ÷ 0.96
ZiggsSquare Ziggs−0.04730.6560.625 ÷ 0.9527
ZileanSquare Zilean00.6250.625 ÷ 1
ZoeSquare Zoe00.6250.625 ÷ 1
ZyraSquare Zyra00.6250.625 ÷ 1