Estimate how much caffeine you drank and how much may still be in your system hours later.
| Total (mg) | – |
| Half-lives | – |
| Approx. remaining (mg) | – |
Use this caffeine calculator after a second espresso when you are wondering whether another cup is a good idea tonight. It is not a medical reading of your liver or a sleep-lab model.
Total milligrams is servings × milligrams each (a drip mug is often about 95 mg, an espresso shot about 63 mg, tea about 40 mg; edit to match what you drink). Remaining caffeine uses a 5-hour half-life: after 5 hours about half is left, after 10 hours about a quarter. That 5-hour figure is a population average for healthy adults, not your metabolism, pregnancy, smoking status, or medication.
Servings: How many servings you had — two mugs, three shots, whatever you are totalling.
mg / serving: Milligrams of caffeine in one serving. 95 is a typical drip cup; type 63 for espresso, 40 for tea.
Hours since last: Hours since you finished that round. Type 5 if it is now late afternoon after a morning coffee.
Total (mg): Sum of caffeine from those servings.
Half-lives: Hours divided by 5.
Approx. remaining (mg): Sketch of caffeine left after that many half-lives.
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