A newborn's stomach is quite small in relation to its body size, reaching only about 1 ounce (28 grams) by the time it's born. This small size allows the stomach to store food and grow slowly in the first few months of life.
According to the chart, a newborn's stomach weighs approximately 3 to 4 ounces (85 to 113 grams) by 1 month old, and 6 to 9 ounces (170 to 212 grams) by 2 months old. By 4 to 6 months old, the stomach has largely grown, weighing between 9 to 12 ounces (260 to 340 grams) and maintaining an average of 10 to 11 ounces (283 to 330 grams).
At around 6 to 9 months old, the newborn's stomach expands to accommodate solid foods, and the weight increases to between 12 to 15 ounces (340 to 403 grams) on average. By the time the baby is 9 to 12 months old, their stomach typically reaches its full size, weighing around 18 to 24 ounces (522 to 688 grams).
