The pH level of an orange varies depending on the type and ripeness of the orange, but generally ranges between 3 and 4. Oranges are considered acidic fruits due to the presence of citric acid, which contributes to their sour taste. The pH scale measures the acidity or alkalinity of a substance on a scale from 0 to 14, with 7 being neutral. Values below 7 indicate acidity, while values above 7 indicate alkalinity. Oranges fall on the acidic side of the scale due to their high concentration of citric acid.