The maximum legal blood alcohol concentration for fully licenced drivers (people who have obtained their G class licence) is 80 milligrams of alcohol in 100 millilitres of blood or 0.08.However, you can also be charged if you are in the warn range , which is between 0.05 to 0.079.
There is a zero tolerance policy (mean you cannot have any alcohol or drugs in your system) in Ontario if you are:
Under the age of 21;
Have a G1, G2, M1, or M2 licence;
Drive a vehicle that requires an A-F driver's licence or Commercial Vehicle Operator's Registration; or
Drive a road-building machine