What is a 'normal amount'? Is there a way of calculating this? I know people who drink three drinks and they are gone. I also know people who drink 6 drinks a

What is a 'normal amount'? Is there a way of calculating this? I know people who drink three drinks and they are gone. I also know people who drink 6 drinks a day, don't black out, get home safe and are fully(seemingly, not sure) functional and productive the next day. Reducing to 'normal' or some level has to be backed up by meaning i think. And that meaning of normal is what I am trying to discover.