160 mg in the standard can
The original green Monster comes in a 16 fl oz can with 160 mg of caffeine, by Monster’s own product information. That is 10 mg per fluid ounce, close to Red Bull’s strength, but in a can nearly twice the size of a standard 8.4 oz Red Bull, so one Monster carries twice the caffeine of that can (80 mg). USDA’s own lab figure for Monster, 33 mg per 100 g, works out to roughly 155 to 160 mg for a 16 oz can, in line with the label.
Guarana counts toward the total
Monster’s recipe includes guarana, which is itself a source of caffeine. The FDA notes that most energy drinks sold in the US list the total caffeine from all sources on the label, including ingredients such as guarana. The 160 mg is the whole dose, not a figure that guarana adds to.
Against coffee and the daily limit
One can is about 1.7 cups of drip coffee at USDA’s reference strength (95 mg per 8 oz), and roughly half a Grande Starbucks Pike Place Roast at the bottom of its range. Two cans, 320 mg, fit under the 400 mg a day the FDA cites for healthy adults; a third takes you to 480 mg.
If a can goes down quickly, the single-dose view is worth knowing. EFSA assessed single doses up to 200 mg as not raising safety concerns for healthy adults. A single 16 oz Monster is under that; two cans in one sitting, 320 mg, are well over it.
Children, teens and pregnancy
The FDA notes that medical experts, citing the American Academy of Pediatrics, advise against energy drinks for children and teens, and that too much caffeine in children and teens can cause increased heart rate, anxiety and sleep problems. In pregnancy, the 200 mg daily ceiling ACOG uses leaves room for one can and very little else: a Monster and a Grande Starbucks decaf (25 mg) already come to 185 mg.