How the caffeine calculator works
The calculator adds up the caffeine from each drink you choose using typical amounts per serving, then compares your total to the 400 mg daily limit that health agencies suggest for most healthy adults. Real amounts vary by brand, bean, brew strength, and cup size, so treat the result as a close estimate rather than an exact figure.
How much caffeine is in common drinks
Average caffeine per serving: brewed coffee about 95 mg per 8 oz, cold brew about 155 mg per 8 oz, a single espresso about 63 mg, instant coffee about 62 mg per 8 oz, and decaf only about 3 mg. For tea, black tea is around 47 mg per 8 oz and green tea around 28 mg. An energy drink runs about 80 mg per 8 oz, a concentrated energy shot about 200 mg, and a cola about 34 mg per 12 oz.
Safe daily caffeine limits
Most health agencies put the safe ceiling for healthy adults at about 400 mg a day, roughly four 8 oz cups of brewed coffee. People who are pregnant are usually advised to stay under 200 mg. Teens and children should have far less, and anyone sensitive to caffeine, or with heart or anxiety conditions, may need to keep well below these numbers. This tool is a guide, not medical advice.
How long caffeine stays in your system
Caffeine has a half-life of about five hours, meaning roughly half is still in your body five hours after you drink it. A 200 mg afternoon coffee can leave around 100 mg in your system at bedtime, which is enough to disturb sleep for many people. To protect sleep, try to finish your last caffeine at least six to eight hours before bed.
Frequently asked questions
How much caffeine is too much? Single doses above about 200 mg can cause jitters, and totals above 400 mg a day raise the odds of a racing heart, anxiety, and poor sleep for most adults.
Does decaf coffee have caffeine? Yes, a little. Decaf is not caffeine free; an 8 oz cup still holds about 3 mg, so several cups can add up.
Is the caffeine in tea different from coffee? The caffeine molecule is identical, but tea usually has less per cup and also contains L-theanine, which many people feel gives a smoother, steadier lift.
Related coffee calculators: Coffee to Water Ratio, Cold Brew, Espresso Yield, Coffee Bean Cost.