Caffeine cutoff calculator
Your 3 pm coffee is still in you at bedtime.
Caffeine leaves your body slowly. Enter when you drink, your bedtime and how much, and see your last safe caffeine time plus how much is left when you turn in.
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How the cutoff is worked out
Caffeine clears in stages. The time for half of a dose to leave your body is its half-life. In most healthy adults that is commonly around five hours, but it can vary from about two hours to around ten, depending on genetics, smoking, pregnancy, some medicines and liver function. The calculator halves the dose once for every half-life that passes between your drink and bedtime.
Why most sleep guides say eight hours
The Sleep Foundation suggests avoiding caffeine at least eight hours before bedtime, and notes that people who are more sensitive may need to stop even earlier. A 2013 controlled study in healthy adults found that caffeine taken six hours before bed still disrupted sleep, so the six-hour mark is the minimum many researchers use. Pick the cutoff that matches how well you sleep, and move it earlier if you wake up at night.
How much is safe in a day?
The Mayo Clinic notes that most healthy adults can have up to about 400 mg of caffeine a day. Pregnancy, certain heart conditions, some medicines and sensitivity to caffeine all change that, so check with a doctor if any of them apply.
Sources for the guidance above: Sleep Foundation, “How long does it take caffeine to wear off”; Drake et al., Journal of Clinical Sleep Medicine, 2013; Mayo Clinic, “Caffeine: How much is too much?”
Wind down on purpose
Give the evening back to you
Sleepward is an iPhone app for people who stay up late because the evening is the only time that feels like theirs. Its four-minute evening reset lets you empty your head into a private Brain Dump and pick up to three things for tomorrow.
Then it protects a stretch of time that is yours, and winds down with a slowly darkening screen and white, pink or brown noise on a fade-out sleep timer. It never scores your sleep and never breaks a streak.
Get Sleepward on the App StoreFree: the evening reset, Brain Dump, tomorrow’s three things, Your Hour, wind-down, sleep logs and white, pink and brown noise. Sleepward Pro is an optional upgrade. No account, no ads. Requires iOS 18 or later. Details checked against the App Store listing on November 10, 2026.
Publisher disclosure: Honest Little Apps publishes both Sleepward and this page. This is not an independent review. This page is a separate web companion, not a feature of the app. This calculator is a rough model using an average half-life. It is not part of the app, not medical advice, and individual caffeine clearance varies widely.
Caffeine and sleep questions
What time should I stop drinking coffee?
Many sleep guides suggest stopping at least eight hours before bed. A 2013 study found that caffeine six hours before bed still disrupted sleep, so the calculator lets you pick a cutoff between four and twelve hours.
How long does caffeine stay in your system?
Caffeine has a half-life that is commonly around five hours in healthy adults, so after about five hours roughly half of a dose is still present, and the remainder keeps declining over the hours that follow.
Does this calculator give medical advice?
No. It is a simple model for planning. Talk to a doctor or pharmacist if you take medicines, are pregnant, or have a condition that caffeine could affect.
Does decaf have caffeine?
Yes, decaf usually has a small amount of caffeine. If you are very sensitive, count it in the evening.
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