Each drink makes its own curve, rising for about 44 minutes and then falling, and the curves add. A mug of filter coffee is 95 mg, a single espresso 63 mg, a small energy drink 80 mg.
The body clears a fixed share each hour, so the amount halves every half-life. A coffee at 3 pm leaves 49 mg at 8 pm and 32 mg at 11 pm.
It is the level when you lie down that counts, not the total for the day. The tool shows both, and the latest time for one more drink that keeps you under a level of your choosing.
Healthy adults range from about 2 to 8 hours. Smoking shortens it; the contraceptive pill and pregnancy lengthen it. Four speeds are drawn side by side for the same day.
A coffee at 3 pm is still about half in you at 8 pm, a quarter at 1 am and an eighth at 6 am.
The amount in you peaks about 45 minutes after the drink, at 90 percent of the dose, because some is already leaving.
A mug of filter coffee leaves 32 mg, and a 200 mg dose leaves 68 mg. Not much, but not nothing.
Smoking shortens it. The contraceptive pill and pregnancy lengthen it, to as much as 16 hours late in pregnancy.
About 4 mugs of filter coffee, and no more than 200 mg at once. In pregnancy the guideline is 200 mg a day.
In a small study, 400 mg six hours before bed cut measured sleep by over an hour, and people did not notice.
A single shot has less caffeine than a mug of filter coffee, though more per mouthful: it is the size that differs.
This is one average model: your half-life is a setting and not a measurement, and the caffeine in a drink varies a lot. It is not medical advice.
Half of it goes about every 5 hours, so after 10 hours a quarter is left and after 15 an eighth. For a healthy adult the half-life is anywhere from about 2 to 8 hours.
A coffee at 3 pm still has about 32 mg in you at 11 pm. In a small study, 400 mg six hours before bed cost over an hour of sleep, even though people did not notice it.
The European Food Safety Authority says up to 400 mg a day, and 200 mg at once, is safe for healthy adults, and 200 mg a day in pregnancy. That is about 4 mugs of filter coffee.
Per mouthful, yes; per cup, no. A single espresso has about 63 mg and a mug of filter coffee about 95 mg, so the mug has half as much again.
It varies with the brew. The Tea & Coffee Brewing Calculator works out the strength of a brew, and the Coffee Grinder Simulator shows how grind size changes it.
It is the same idea, a curve through the day, but the body clears them differently. The Blood Alcohol Curve burns alcohol off at a steady rate; caffeine falls by a fixed share each hour.
Because your half-life may be longer. Genes, the contraceptive pill, pregnancy and some medicines slow it; smoking speeds it up. Try the slow settings under “Your body”.
A little: usually a few milligrams a cup, not none. It is small next to the 95 mg of a mug of filter coffee, but it adds up if you drink a lot of it.
No. The liver clears caffeine at its own pace, and neither water nor food speeds that up.
This page has changed in 1 archived release, but each of those was a site-wide pass, so none is attributable to this tool on its own and none is listed here. That is not a claim that the tool never changed — a release that reworked many pages at once may well have altered this one too. The changelog has them.