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Caffeine Cutoff Calculator

What time to stop caffeine, based on your bedtime and caffeine's ~5-hour half-life.

Not medical advice. This tool gives a general estimate for informational purposes only — it does not replace professional judgment. If you're concerned, contact a doctor right away. Caffeine metabolism varies a lot by person (pregnancy, smoking, medications, and liver function all change it) — this uses a population-average half-life, not a measurement of how you personally process caffeine.

We work backward from this using caffeine's ~5-hour half-life.

Sources & how this is calculated

Caffeine leaves your system on a predictable decay curve, not a sudden cutoff. Its mean elimination half-life is about 5 hours in healthy adults — meaning roughly half of what you drank is still active 5 hours later, a quarter after 10 hours, and so on — per the NIH/NCBI Bookshelf's StatPearls entry on caffeine. Individual half-life varies widely (roughly 1.5 to 9.5 hours) depending on pregnancy, smoking, liver function, and other medications, which is why this is a population-average estimate, not a personal measurement.

The three cutoff options above use exact half-life multiples: 1 half-life (5h before bed) leaves about half the caffeine active, 2 half-lives (10h before bed, our recommended default) leaves about a quarter active, and 3 half-lives (15h before bed) leaves under an eighth active for people who are more caffeine-sensitive. This is a somewhat more conservative default than the commonly-cited "stop at least 8 hours before bed" rule of thumb from the Sleep Foundation's "Caffeine and Sleep Problems" — at 8 hours before bed with a 5-hour half-life, only about a third of the caffeine has actually cleared. The FDA's "Spilling the Beans" guidance separately notes it typically takes 4-6 hours to metabolize half of what you consumed, consistent with the 5-hour figure used here, and that up to 400 mg/day is generally not associated with dangerous effects for healthy adults.

This is a general estimate, not a measurement of your own metabolism — how caffeine affects your sleep also depends on the amount you drink and your personal sensitivity, not just timing.