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.
Liquid fuel measurements and conversions. Gasoline. 1 gallon = 125,000 Btu â HHV *. 1 gallon = 131.9 megajoules â HHV *. 1 gallon = 115,400 Btu â LHV *. 1 gallon = 121.7 megajoules â LHV *. 1 gallon = .002791 metric tons. 1 barrel = 5,250,000 Btu â HHV *.