* Conversion: 1 gallon = 3.785 liters

* Half Liters: 1 liter = 2 half liters

Calculation:

1. Convert gallons to liters: 3.785 liters/gallon * 1 gallon = 3.785 liters

2. Convert liters to half liters: 3.785 liters * 2 half liters/liter = 7.57 half liters

Answer: There are approximately 7.57 half liters in a gallon.