Up to 400 mg a day suits many adults; pregnancy caps at 200 mg, and teens often do better with less.

A 12-oz (355 mL) can of Coca-Cola has 34 mg of caffeine in the U.S.

Most decaf teas land in the 2–5 mg caffeine range per 8-oz cup, with a few brews creeping closer to 10 mg.

A 12-oz can of Dr Pepper lists 41 mg of caffeine per serving.

Decaf coffee still carries caffeine—often 2–15 mg per 8 oz cup, with some cups running higher.

Cold brew caffeine can land anywhere from about 90 mg to 300+ mg per 12 oz, based on the recipe, the beans, and how the drink is diluted.

Most pregnancy guidelines cap caffeine at 200 mg per day, which is often around one 12-oz brewed coffee.

A typical 8-ounce mug of brewed green tea lands around 30–50 mg of caffeine, with steep time, leaf dose, and tea style driving the swing.

A 12-oz (355 mL) can of Diet Coke has 46 mg of caffeine in the U.S.

A standard 12-oz (355 mL) can of Coca-Cola contains about 34 mg of caffeine.