Free Tool
Caffeine Cutoff Calculator
Free here • Paid in Sleep coaching apps, Calm/Headspace adjacent
Caffeine has a half-life around 5 hours. That afternoon coffee is still 25 percent in your system at midnight. Enter your dose and bedtime to see what is left when you try to sleep.
Your caffeine intake
At bedtime
Caffeine still active
27 mg
Below the 50 mg threshold. Sleep impact should be minor.
Hours to clear
Under 50 mg in 4.6 h
Under 25 mg in 9.6 h
Recommended cutoff times
Based on a 95 mg dose and a 5 hour half-life, working backwards from your 11:00 PM bedtime.
Decay curve
Caffeine remaining after your last dose.
| Hours after dose | Caffeine remaining | % of dose |
|---|---|---|
| +0 h | 95.0 mg | 100% |
| +1 h | 82.7 mg | 87% |
| +2 h | 72.0 mg | 76% |
| +3 h | 62.7 mg | 66% |
| +4 h | 54.6 mg | 57% |
| +5 h | 47.5 mg | 50% |
| +6 h | 41.4 mg | 44% |
| +7 h | 36.0 mg | 38% |
| +8 h | 31.3 mg | 33% |
| +9 h | 27.3 mg | 29% |
| +10 h | 23.8 mg | 25% |
| +11 h | 20.7 mg | 22% |
| +12 h | 18.0 mg | 19% |
Get personalized caffeine reminders based on your sleep schedule in Zealova
Zealova learns your bedtime, tracks every coffee, and pings you when you are approaching your daily cutoff.
Free 7-day trial. $7.99/mo or $59.99/yr after. Cancel anytime.
Methodology + Sources
- Drake CL, Roehrs T, Shambroom J, Roth T (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine 9(11):1195-1200.
- O'Callaghan F, Muurlink O, Reid N (2018). Effects of caffeine on sleep quality and daytime functioning. Risk Management and Healthcare Policy 11:263-271.
- Institute of Medicine (2001). Caffeine for the Sustainment of Mental Task Performance. National Academies Press. Reference half-life range 3-7 hours.
Last updated: 2026-05-14
Built by Sai, founder of Zealova. Not a neutral third party. Calculator results are estimates. For medical decisions, consult a qualified professional.
Frequently asked questions
How long does caffeine stay in your system?+
Half-life averages 5 hours in healthy adults, with a normal range of 3 to 7 hours. That means after 5 hours, half the dose is still active. After 10 hours, 25 percent. Genetics, age, smoking status, pregnancy, and certain medications can push your personal half-life outside that range.
What is a safe amount of caffeine at bedtime?+
Drake and colleagues found that 400 mg of caffeine taken 6 hours before bed still cut total sleep time by more than an hour. To minimize impact, aim for under 50 mg in your system at bedtime, and under 25 mg if you are caffeine-sensitive.
Why does my coffee not seem to keep me up?+
You may still be experiencing reduced sleep depth even when you fall asleep fine. Studies show caffeine taken 6 hours before bed reduces objectively measured sleep efficiency without changing subjective sleep quality. You feel rested but your brain got less deep sleep.
Does this account for tolerance?+
No. The half-life calculation is pharmacokinetic and does not change with tolerance. Tolerance affects how alert you feel from a given dose, not how long the molecule stays in your bloodstream. The mg-at-bedtime number is the same whether you drink coffee daily or never.
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