How it works
In three steps
- 01 In
Caffeine from each drink reaches your blood within about an hour, spread across however long it took you to drink it.
- 02 Out
Your body then clears it gradually: for a typical adult, half is gone after about 5 hours. Your answers on Make it more accurate adjust that. Every drink adds up into one curve.
- 03 Bedtime
The curve is compared with your sleep-friendly level at bedtime and through the night. That gives the number at bedtime, when you are back under it, and the latest time each drink still fits.
It is an estimate from averages, not a measurement. For what caffeine does to sleep, see What the research says.
See an example day
Not sure what you'll see? Load a sample day: a morning coffee, an espresso, a tea and a diet cola. It's clearly marked as an example and one tap clears it.
What the research says
- In a sleep-lab trial, 400 mg of caffeine taken 6 hours before bed cut sleep by more than an hour, and people often did not notice. Drake et al., 2013
- A 2023 meta-analysis found caffeine cut total sleep by about 45 minutes, and suggested stopping about 8.8 hours before bed for a cup of coffee and 13.2 hours for a pre-workout dose. Gardiner et al., 2023
- The FDA cites 400 mg a day as an amount not generally associated with negative effects for most healthy adults. FDA
These are group averages. CaffeineIQ does not estimate how much sleep you personally lose.
Not medical advice
CaffeineIQ is an estimate built on average pharmacokinetics and published caffeine figures. Real levels vary with genetics, health, food and medication. It does not diagnose or treat anything. If you have a health condition, are pregnant, or take medication, talk to a clinician.
Your data stays in this browser. Nothing is sent anywhere. Data: brand pages, USDA FoodData Central, DailyMed, Open Food Facts (world.openfoodfacts.org, Open Database License) and published caffeine tables; every row links to its source on the All drinks page.
CaffeineIQ for iPhone
The iPhone app is coming soon. Everything on this page keeps working without it.
- Your bedtime number on the lock screen. A widget shows the caffeine left at bedtime and your cutoff.
- See what caffeine does to your sleep. It compares your nights using Apple Health, on your phone.
- A nudge before your cutoff. A reminder before the latest time your usual drink still fits.
About
CaffeineIQ is made by C6 Labs. The web tool is free and runs entirely in your browser.
Chart style inspired by caffeine-day by Charles Postiaux (MIT).