The weight of a gallon of milk can vary depending on the type of milk and its fat content. Here are some approximate weights for common types of milk:

- Whole milk: A gallon of whole milk weighs about 8.6 pounds (3.9 kilograms).
- Skim milk: A gallon of skim milk weighs about 8.3 pounds (3.8 kilograms).
- 2% milk: A gallon of 2% milk weighs about 8.5 pounds (3.9 kilograms).
- Chocolate milk: A gallon of chocolate milk weighs about 8.6 pounds (3.9 kilograms).

It’s important to note that these weights are approximate and can vary based on factors such as the temperature and density of the milk. Additionally, different brands of milk may have slightly different weights due to variations in packaging and processing.