What's actually in the can
Energy drinks typically contain 80-300 mg of caffeine per can. A standard 8.4 oz can lands around 80 mg — similar to a cup of coffee. The larger or "extreme" cans, and the concentrated shots, can reach 200-300 mg, which is close to the entire daily guideline for a healthy adult in one serving.
The label matters more than the can size. Two cans of the same brand can differ in caffeine if they are different sizes, so check the caffeine per serving and the number of servings per can.
Caffeine is only part of it
Beyond caffeine, many energy drinks add taurine, sugar, and large doses of B vitamins. The sugar gives a fast lift and a later crash, and the combination can feel stronger than the caffeine alone. For sleep, the caffeine is the ingredient that lingers longest — it is still in your system hours after the sugar rush fades.
Compared to coffee, a single large energy drink can equal two or three cups. If you are drinking one after mid-afternoon, use the half-life calculator to see how much is still around at bedtime.
Quick answers
Which drink has the most caffeine?
Energy drinks and large brewed coffees top the list; a large drip coffee can hold 200-300 mg.
Does tea have less caffeine than coffee?
Usually yes — black tea has about half the caffeine of a similar cup of coffee.
Is decaf caffeine-free?
No, decaf still has a small amount, usually 2-15 mg per cup.
Why do numbers differ online?
Brewing strength, bean type, and brand all change the amount. Treat numbers as ranges.
Does cold brew have more caffeine?
Usually yes per cup, because it is more concentrated than drip coffee.