The pH of the stomach ranges between 1 and 5, according to About. The exact pH of the stomach varies according to the types and quantities of food that have been eaten recently.
About states that the pH of the stomach is lowest in the morning before a person eats breakfast and highest after a person eats a meal high in protein. Lower pH values indicate that the fluid in the stomach is more acidic. A stomach acid test measures the acidity of an empty stomach, according to MedlinePlus, which advises that the normal result of this test is a pH between 1.5 and 3.5.