Caffeine Flow - Caffeine Half-Life Calculator & Sleep Tracker
Free caffeine half-life calculator and tracker for iPhone and Android. Graph the caffeine left in your body, see when it's safe to sleep, and log 180+ drinks.
"Love coffee, but worried about tonight's sleep?"
What matters most isn't just when you drink coffee, but how long caffeine lingers in your body. Caffeine Flow is a caffeine half-life calculator and daily caffeine tracker in one: it applies the half-life formula to every drink you log, graphs your caffeine level in real time, and pinpoints your Safe Sleep Gate so you wake up refreshed.
⏱️ Live Caffeine Half-Life Graph
See how much caffeine is left in your body right now, plus a 24-hour curve that shows when you'll be ready for sleep.
✨ Caffeine Sensitivity Profile
A quick quiz finds your metabolism type (Elephant, Human, or Rabbit) and, with your weight, sets your daily limit and sleep threshold.
☕ Coffee Caffeine Content Database
Log in seconds with 180+ cafe chain drinks, canned coffees, and energy drinks, including official cup sizes like Tall and Venti.
🔔 Caffeine Sleep Alerts
Get a heads-up when your projected bedtime caffeine level could disturb your sleep, or when you go over your daily limit.
📱 Widgets & Conveniences
Features home screen widgets for tracking without opening the app, smooth navigation, and a clean statistical dashboard.
What Is Caffeine Half-Life? Formula and Example
Caffeine half-life is the time it takes your body to clear half of the caffeine you consumed. In healthy adults it averages about 5 hours, typically somewhere between 3 and 7 hours. It tends to run longer during pregnancy and shorter in smokers, and it can also shift with certain medications or liver function.
Caffeine half-life formula
Remaining caffeine = initial dose × (1/2)hours elapsed ÷ half-life
Example: 200 mg at 9 AM (5-hour half-life)
| Time | Hours elapsed | Caffeine left |
|---|---|---|
| 9:00 AM | 0 | 200 mg |
| 2:00 PM | 5 | ~100 mg |
| 7:00 PM | 10 | ~50 mg |
| Midnight | 15 | ~25 mg |
Even a morning coffee can leave about a quarter of its caffeine in your system at midnight. Caffeine Flow does this math for every drink automatically and turns it into a caffeine graph and a sleep-ready time.
This is general information, not medical advice. If you are pregnant, have a health condition, or take medication, talk to a healthcare professional.
Frequently Asked Questions
Find quick answers to common questions about this app.
Q. What is the half-life of caffeine?
In healthy adults it averages about 5 hours, with a typical range of roughly 3 to 7 hours. It tends to be longer during pregnancy and shorter in smokers, and it can also change with certain medications or liver function.
Q. How do you calculate caffeine half-life?
Use remaining caffeine = initial dose × (1/2)^(hours elapsed ÷ half-life). With a 5-hour half-life, 200 mg drops to about 100 mg after 5 hours and about 50 mg after 10 hours. Caffeine Flow runs this for every drink you log and adds them up on a live graph.
Q. How many hours before bed should I stop drinking coffee?
It varies from person to person, but a common recommendation is to avoid caffeine for at least 6 hours before bed. With a 5-hour half-life, half of a 3 PM coffee is still in your system at 8 PM. Caffeine Flow uses your weight, sensitivity, and bedtime to show when it's safe to sleep and when to have your last cup.
Q. How does Caffeine Flow predict my safe sleep time (Sleep Gate)?
It sets a personal sleep-safe threshold from your weight and caffeine sensitivity, then uses the half-life formula to find when your body level falls below it. Your half-life is set to 4, 5, or 7 hours based on a quick sensitivity quiz, with 5 hours as the default.
Q. How much caffeine is in a cup of coffee?
It depends heavily on the brand and cup size. In Caffeine Flow's drink data, one espresso shot at major chains ranges from roughly 50 to 120 mg, so a single americano can contain anywhere from about 75 mg to over 400 mg. The app includes 180+ drinks, from Starbucks and other cafe chains to canned coffees and energy drinks like Red Bull and Monster, and you can add your own.
Q. How much caffeine per day is safe?
Up to 400 mg a day is generally considered safe for healthy adults. Caffeine Flow tailors your daily limit to your weight, sensitivity, and whether you are pregnant or a teenager, and alerts you when you go over it.
Q. Is Caffeine Flow free?
Yes. It's free to download with no in-app purchases; the app is supported by ads.
Q. Does it work on both iPhone and Android?
Yes, it's available on iOS (App Store) and Android (Google Play). Your logs stay on your device, and you can move them to a new phone with the built-in backup and restore.