The classic way to convey the error that exists in a measurement is a formula that shows the obtained measurement (X) as a sum of a true score plus some error. One version of this formula is: X = T + e. With this formula in mind, obtaining more precise measures depends on reducing error.
  Mega is the prefix meaning one million, therefore there are one million (1,000,000) gallons in a mega gallon.
It is rather easy to convert gallons to ounces and vice versa. The question to the answer, âHow many OZ are in a gallon?â is that one gallon has 128 ounces. But this answer is correct only if you mean US liquid gallons and US fluid ounces. And there are some other definitions of these units, so you should know the most important of them in order not to get confused.