USDA’s reference figure for a can of cola
USDA measures regular carbonated cola at 9 mg of caffeine per 100 g, which comes to about 33 mg in a standard 12 fl oz can, 44 mg in a 16 fl oz bottle and 89 mg in a 32 fl oz large fountain drink. Because the figure scales with volume, a gas-station or movie-theater fountain cola can carry two or three times a can’s caffeine simply by being poured bigger, with nothing about the recipe changing.
This generic figure sits close to named brands rather than standing apart from them. Coca-Cola carries 34 mg per 12 oz can by the Coca-Cola Company’s own figures, just above USDA’s generic number, and Pepsi carries 38 mg. Diet Pepsi, at 35 mg, is closer still. A generic store-brand cola without its own published figure is reasonably estimated from USDA’s number if the label doesn’t list caffeine directly.
Fountain sizes change the math
A can and a bottle are close enough in caffeine per ounce that swapping between them barely matters, but fountain sizes break that pattern. A 32 oz large fountain cola at 89 mg carries more caffeine than a can and a bottle combined, and gets there in one cup with a single price tag and no serving-size cue on the container the way a can provides. It’s also closer to a full cup of drip coffee (95 mg at USDA’s reference strength) than most people expect from a soda.
Where it fits
At USDA’s 33 mg per can, twelve cans stay under the 400 mg daily figure the FDA cites for healthy adults, well past what anyone would actually drink in a day. The large fountain size is the one to watch: two of them, 178 mg, already approach half that daily figure, and in pregnancy a single 32 oz fountain cola uses close to half the 200 mg daily ceiling ACOG uses.