How long does caffeine stay in your system?
Caffeine leaves by halves, not all at once. Half of a coffee’s caffeine is still in you about five hours later — a quarter after ten.
Half of a drip coffee (48 mg) is still with you 5 hours after the last sip. You slip under 50 mg about 4 hours 40 minutes in.
| When | Still in you |
|---|---|
| Last sip | 95 mg |
| 5 hours later | 48 mg |
| 10 hours later | 24 mg |
| 15 hours later | 12 mg |
The halves, in plain words
The FDA puts the typical caffeine half-life at four to six hours; most people land near five. "Half-life" just means the time it takes your body to clear half of whatever caffeine is on board. Five hours after a 95 mg cup of drip, about 48 mg is left. Five hours after that, about 24 mg. The amount never snaps to zero — it fades by halves until it stops mattering.
That's why an early-afternoon coffee can still show up at bedtime. It isn't that caffeine "lasts eight hours" exactly — it's that a big enough starting number, cut in half once or twice, is still a real number at 11 pm.
Coffee, tea, cola — same clock
The half-life belongs to the caffeine, not the drink. A 47 mg cup of black tea and a 47 mg glass of cola fade on the same schedule as 47 mg worth of coffee. What differs is the starting number — and those vary a lot more than people expect. A 12-oz cold brew carries about twice the caffeine of the same cup of drip. The drinks table has the real figures, each with its source.
Want the other direction — the latest time to finish a drink and still sleep? That's the cutoff calculator.
Common questions
Is caffeine out of my system after ten hours?
Not quite. Ten hours is about two half-lives for most people, which leaves roughly a quarter of what you drank — 50 mg of a strong 200 mg cold brew. Whether that quarter matters depends on how big the drink was and how lightly you sleep.
Do bigger drinks take longer to wear off?
The halving pace stays the same — five hours is five hours. But starting higher means more is left at every hour after. Half of a 310 mg Starbucks grande is 155 mg, which is still more than a whole cup of drip.
Does decaf count?
Barely. A cup of decaf drip carries about 2 mg — there is a trace, but the bedtime math hardly notices. Watch out for "half-caf" though, which is exactly what it sounds like.
Why does my friend metabolize coffee faster than me?
The speed is set mostly by a liver enzyme, and people are simply built differently. Smoking speeds it up; pregnancy and some medications slow it down a lot; age and genetics do the rest. That spread is why the published range is four to six hours rather than one tidy number.