When a measurement is being described in a sentence, that quantity takes a singular verb form.
In such cases, the entire quantity is thought of as a single entity that should be considered together, not separately. See the following examples, in which the entire sample was added or tested at a single time:
In total, 10g of tissue was tested. (NOT: 10g of tissue were tested)
Five milliliters of solvent was added to the mixture. (NOT: Five
milliliters were added)
Your examples are like those above. They are measured quantities, so they should use "is." In fact, I would argue that the last example, the one that says "16 ounces," should use "is," not "are."
"Calories" is another matter. A calorie is an International System of Units (ISU) measure of heat, like a meter is for distance. The word "calories" when it refers to food is actually short for "kilocalories," a thousand times the heat energy of an actual calorie, but I digress. Just like with grams, millimeters, etc., when a measurement in calories is being described in a sentence, it should really call for a singular verb conjugation, like "is," but for whatever reason, people so often use a plural verb conjugation, like "are," instead that I'm reluctant to call it a grammatical error since English grammar is descriptive, not prescriptive, so I'll just go so far as to say the usage of the plural verb "are" in that example is irregular in the sense that it is inconsistent with how we normally express measurements. Still, what I myself would say, along with many others, is, "There's about 125 calories in a banana," not, "There are about 125 calories in a banana."