The adult human stomach weighs roughly 2 pounds when it is completely empty. However, its exact size and weight varies for each person, therefore only an approximate value can be determined.
The stomach is highly muscular in nature, therefore it is able to contain large quantities of food and drink when required. The stomach does this by expanding outwards, enabling it to contain up to 4 liters of digested food and drink. This results in a weight over five times greater than when it was empty. Converted into weight, 4 liters equals almost 9 pounds, therefore it is possible for the human stomach to weigh 11 pounds after an incredibly large meal.