About 80 mg per 8.4 oz can
The standard 8.4 oz (250 ml) can of Red Bull contains roughly 80 mg of caffeine — about the same as a single cup of coffee. The bigger 12 oz can has around 114 mg, and the 16 oz around 151 mg. Compare it on the caffeine chart. (Per the standard can; check the label for the size you have.)
Why it feels stronger than it is
Red Bull's kick isn't really about the caffeine — at 80 mg it's a modest dose. It's the sugar (~27 g in a standard can), the cold fizzy delivery, and the fact people drink it fast. The sugar-free version keeps the 80 mg and drops the sugar.
How it fits your day
One standard can is an easy fit inside the 400 mg adult limit — it's roughly a quarter of it. Where it adds up is in combination: a Red Bull plus two coffees is already ~270 mg. Track the total with the intake calculator.
And your sleep
80 mg is gentler than a Monster or cold brew, but it's still caffeine. An evening Red Bull — common before nights out or gaming sessions — will keep working long past when you want to sleep. Check what's left at bedtime with the half-life calculator.
Put it into practice: see how a Red Bull stacks up against your coffee on the caffeine chart.