Flex fuel ethanol calculator

Fuel
Gasoline ethanol content   %
E85 ethanol content   %
Vehicle
Fuel tank size   gallons
Current fuel level   %
Ethanol
Current ethanol content   %
Desired ethanol content   %
Results
E85   gallons
Gasoline   gallons
Final ethanol   %

This calculates what blend of gasoline and E85 you need in order to get the right ethanol content in you tank.