A peg is an informal unit of measurement of alcoholic spirits. Measures 1 to 2 fluid ounces (30-60 ml). In some jurisdictions the "peg" is a standardized measure. 1 unit of peg = 30ml whiskey = 100 ml wine = 250 ml beer. So now you know how much a peg is but actually it doesn’t matter, just keep the tab rolling and gobble down.