What is the most popular retail size container for fluid milk in the U.S.?

The most popular retail size container for fluid milk in the U.S. is the gallon. This is primarily due to consumer preferences for purchasing larger quantities, especially for families and households that consume milk regularly. The gallon size is convenient for storage and usage within the home and is often the most cost-effective option for consumers compared to smaller containers. Additionally, the gallon container is a standard size in grocery stores, making it easily recognizable and readily available for consumers.

While half-gallon, quart, and liter containers are also sold, they cater more to specific consumer needs, such as smaller households or those looking for more variety in milk types, which can reduce waste if the milk is not consumed quickly. The gallon size thus stands out as the preferred choice for its practicality and value.