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Last-coffee calculator

Pick a drink, when you had it (or plan to), and your bedtime. You get the caffeine still circulating at lights out, and the latest time that keeps it under 25 mg.

Updated October 3, 2026 · FDA · USDA · IOM 2001 · Drake 2013

At bedtime you would still have:

remaining = dose × 0.5^(hours ÷ 5). Half-life varies 1.5–9.5 h between people. How we calculate

Caffeine left after one 96 mg cup of brewed coffee
0h2h4h6h8h10h12h964824half gone at 5 h

Half-life 5 h (IOM 2001); shaded = FDA 4–6 h

How to read the result

Caffeine leaves the body by halves — about every five hours for a typical adult (the FDA cites four to six). The 25 mg line is a planning threshold used on this site, roughly a quarter cup of coffee, not a medical limit. The third figure is the six-hour cutoff from the only controlled trial on timing, in which a 400 mg dose six hours before bed still cut sleep by over an hour.

Pages by drink and by bedtime: caffeine by drink · cutoff by bedtime.

Sources

  1. Caffeine content for coffee, tea, soda and more — Mayo Clinic
  2. Spilling the Beans: How Much Caffeine is Too Much? — U.S. Food and Drug Administration
  3. FoodData Central — U.S. Department of Agriculture
  4. Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed — J Clin Sleep Med 9(11):1195-1200, 2013 (Drake C. et al.)
  5. Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations — National Academies Press, 2001

General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.