Attack delay is the hidden variable that is used to calculate a champion's "base attack speed".

Base attack speed = 0.625 / (1 + attack delay)

Champion	Attack delay	Calculated base attack speed
		Decimal (mouseover for expansion)	Precise fraction
Ahri Ahri	−0.065	0.668	0.625 / 0.935
Akali Akali	−0.1	0.694	0.625 / 0.9
Alistar Alistar	0	0.625	0.625 / 1
Amumu Amumu	−0.02	0.638	0.625 / 0.98
Anivia Anivia	0	0.625	0.625 / 1
Annie Annie	0.08	0.579	0.625 / 1.08
Ashe Ashe	−0.05	0.658	0.625 / 0.95
Blitzcrank Blitzcrank	0	0.625	0.625 / 1
Brand Brand	0	0.625	0.625 / 1
Caitlyn Caitlyn	0	0.625	0.625 / 1
Cassiopeia Cassiopeia	−0.03	0.644	0.625 / 0.97
Cho'Gath Cho'Gath	0	0.625	0.625 / 1
Corki Corki	−0.05	0.658	0.625 / 0.95
Darius Darius	−0.08	0.679	0.625 / 0.92
Diana Diana	0	0.625	0.625 / 1
Dr. Mundo Dr. Mundo	0	0.625	0.625 / 1
Draven Draven	−0.08	0.679	0.625 / 0.92
Elise Elise	0	0.625	0.625 / 1
Evelynn Evelynn	−0.05	0.658	0.625 / 0.95
Ezreal Ezreal	−0.06	0.665	0.625 / 0.94
Fiddlesticks Fiddlesticks	0	0.625	0.625 / 1
Fiora Fiora	−0.07	0.672	0.625 / 0.93
Fizz Fizz	−0.05	0.658	0.625 / 0.95
Galio Galio	−0.02	0.638	0.625 / 0.98
Gangplank Gangplank	−0.04	0.651	0.625 / 0.96
Garen Garen	0	0.625	0.625 / 1
Gragas Gragas	−0.04	0.651	0.625 / 0.96
Graves Graves	0	0.625	0.625 / 1
Hecarim Hecarim	−0.0672	0.67	0.625 / 0.9328
Heimerdinger Heimerdinger	0	0.625	0.625 / 1
Irelia Irelia	−0.06	0.665	0.625 / 0.94
Janna Janna	0	0.625	0.625 / 1
Jarvan IV Jarvan IV	−0.05	0.658	0.625 / 0.95
Jax Jax	−0.02	0.638	0.625 / 0.98
Jayce Jayce	−0.05	0.658	0.625 / 0.95
Karma Karma	0	0.625	0.625 / 1
Karthus Karthus	0	0.625	0.625 / 1
Kassadin Kassadin	−0.02	0.638	0.625 / 0.98
Katarina Katarina	−0.05	0.658	0.625 / 0.95
Kayle Kayle	−0.02	0.638	0.625 / 0.98
Kennen Kennen	−0.0947	0.69	0.625 / 0.9053
Kha'Zix Kha'Zix	−0.06	0.665	0.625 / 0.94
Kog'Maw Kog'Maw	−0.06	0.665	0.625 / 0.94
LeBlanc LeBlanc	0	0.625	0.625 / 1
Lee Sin Lee Sin	−0.04	0.651	0.625 / 0.96
Leona Leona	0	0.625	0.625 / 1
Lissandra Lissandra	?	?	?
Lulu Lulu	0	0.625	0.625 / 1
Lux Lux	0	0.625	0.625 / 1
Malphite Malphite	−0.02	0.638	0.625 / 0.98
Malzahar Malzahar	0	0.625	0.625 / 1
Maokai Maokai	−0.1	0.694	0.625 / 0.9
Master Yi Master Yi	−0.08	0.679	0.625 / 0.92
Miss Fortune Miss Fortune	−0.05	0.658	0.625 / 0.95
Mordekaiser Mordekaiser	−0.1	0.694	0.625 / 0.9
Morgana Morgana	0.08	0.579	0.625 / 1.08
Nami Nami	−0.03	0.644	0.625 / 0.97
Nasus Nasus	−0.02	0.638	0.625 / 0.98
Nautilus Nautilus	0.02	0.613	0.625 / 1.02
Nidalee Nidalee	−0.07	0.672	0.625 / 0.93
Nocturne Nocturne	−0.065	0.668	0.625 / 0.935
Nunu Nunu	0	0.625	0.625 / 1
Olaf Olaf	−0.1	0.694	0.625 / 0.9
Orianna Orianna	−0.05	0.658	0.625 / 0.95
Pantheon Pantheon	−0.08	0.679	0.625 / 0.92
Poppy Poppy	−0.02	0.638	0.625 / 0.98
Quinn Quinn	−0.065	0.668	0.625 / 0.935
Rammus Rammus	0	0.625	0.625 / 1
Renekton Renekton	−0.06	0.665	0.625 / 0.94
Rengar Rengar	−0.08	0.679	0.625 / 0.92
Riven Riven	0	0.625	0.625 / 1
Rumble Rumble	−0.03	0.644	0.625 / 0.97
Ryze Ryze	0	0.625	0.625 / 1
Sejuani Sejuani	−0.0672	0.67	0.625 / 0.9328
Shaco Shaco	−0.1	0.694	0.625 / 0.9
Shen Shen	−0.04	0.651	0.625 / 0.96
Shyvana Shyvana	−0.05	0.658	0.625 / 0.95
Singed Singed	0.02	0.613	0.625 / 1.02
Sion Sion	0	0.625	0.625 / 1
Sivir Sivir	−0.05	0.658	0.625 / 0.95
Skarner Skarner	0	0.625	0.625 / 1
Sona Sona	−0.03	0.644	0.625 / 0.97
Soraka Soraka	0	0.625	0.625 / 1
Swain Swain	0	0.625	0.625 / 1
Syndra Syndra	0	0.625	0.625 / 1
Talon Talon	−0.065	0.668	0.625 / 0.935
Taric Taric	0	0.625	0.625 / 1
Teemo Teemo	−0.0947	0.69	0.625 / 0.9053
Thresh Thresh	0	0.625	0.625 / 1
Tristana Tristana	−0.05	0.658	0.625 / 0.95
Trundle Trundle	−0.07	0.672	0.625 / 0.93
Tryndamere Tryndamere	−0.03	0.644	0.625 / 0.97
Twisted Fate Twisted Fate	−0.04	0.651	0.625 / 0.96
Twitch Twitch	−0.08	0.679	0.625 / 0.92
Udyr Udyr	−0.05	0.658	0.625 / 0.95
Urgot Urgot	−0.03	0.644	0.625 / 0.97
Varus Varus	−0.05	0.658	0.625 / 0.95
Vayne Vayne	−0.05	0.658	0.625 / 0.95
Veigar Veigar	0	0.625	0.625 / 1
Vi Vi	−0.03	0.644	0.625 / 0.97
Viktor Viktor	0	0.625	0.625 / 1
Vladimir Vladimir	−0.05	0.658	0.625 / 0.95
Volibear Volibear	0	0.625	0.625 / 1
Warwick Warwick	−0.08	0.679	0.625 / 0.92
Wukong Wukong	−0.05	0.658	0.625 / 0.95
Xerath Xerath	0	0.625	0.625 / 1
Xin Zhao Xin Zhao	−0.07	0.672	0.625 / 0.93
Yorick Yorick	0	0.625	0.625 / 1
Zac Zac	0	0.625	0.625 / 1
Zed Zed	−0.05	0.658	0.625 / 0.95
Ziggs Ziggs	−0.04734	0.656	0.625 / 0.95266
Zilean Zilean	0	0.625	0.625 / 1
Zyra Zyra	0	0.625	0.625 / 1