How much caffeine is in what
A standard 240 ml cup of drip coffee carries about 95 mg of caffeine, a single espresso shot 63 mg, and black tea around 47 mg. Energy drinks land near 80 mg per 250 ml can, cola near 34 mg per 355 ml, and a cup of matcha around 70 mg — gentler than coffee because the leaf is steeped rather than brewed hard. Real-world drinks vary: a large café coffee or a strong cold brew can hold two or three "cups" worth in one go.
Limits and the half-life clock
The FDA points healthy adults at no more than 400 mg a day, teenagers at about 100 mg, and pregnancy guidance usually settles near 200 mg. Caffeine leaves the body on a roughly 5.7-hour half-life: enter the hours since your last drink and the calculator shows what remains — half after one half-life, a quarter after about eleven and a half. That lingering quarter is why a 4 p.m. espresso can still be nudging your sleep at midnight.
Frequently Asked Questions
How long until caffeine wears off completely?
Never fully zero, but the effect fades fast in relative terms: about half is gone in 5–6 hours for most adults, and under 10% remains after a full day. Genetics, smoking, medications, and liver health shift the half-life between people.
Is 400 mg safe for everyone?
No — it is the figure for healthy adults. Pregnant people are usually advised toward 200 mg, teens toward 100 mg, and anyone with heart arrhythmia, anxiety disorders, or certain medications should set a personal limit with their doctor.
Does espresso have more caffeine than coffee?
Per ounce, dramatically — but a serving is one small shot at 63 mg versus a full cup of drip at about 95 mg. The small cup is why espresso drinks often end up gentler than a big mug of filter coffee.