To last hit under tower in 6.22 you need 87-91 AD at level 1
Currently you need ~ 7-19% Attack Speed, Dorans Blade, +5 to creeps from masteries, and between base+8-12(Runes) to last hit under turret at level 1-7. This can be a combination of ; 14% Atk speed 8.5 AD 9 Armor +MR ; 15 AD, 9 Armor + MR ; 20% Atk speed 8.5 AD, 9 Armor + No MR
MELEE ~45% health per bullet RANGED ~70% health per bullet SIEGE ~14% health per bullet SUPER ~5% health per bullet
Melee minion - Health 455 (+15 at 3 mins, +15.2 at 4.5 mins, +15.4 at 6 mins,...) 455 *.1 = 45.5 HP After 2 shots
Ranged Minion - Health 290 (+11 at 3 mins, +11.2 at 4.5 mins, +11.4 at 6 mins,...) 290 *.3 = 87
Siege Minion - Health 805 (+23 at 3min, +23.3 at 4.5min, +23.6 at 6min,...) 6 Turret shots *.14 (84%) = 129 (Casters/Melees will auto it atleast once during a wave crash) 129 + 23 Dmg from a caster minion (103) + 12 Dmg from a melee minion = ~91