Doppio frequently asked questions
Short answers about how Doppio works. For the full method, see how Doppio calculates caffeine.
How does Doppio know how much caffeine is in my body?
Every drink you log is decayed over time with a half-life model: the caffeine left from a drink is its amount times 0.5 raised to (hours since drinking divided by your half-life). Doppio adds up all of today's and recent drinks to show the level in your system right now and how it fades over the hours ahead.
What half-life does Doppio use?
The default is 5 hours, a typical value for healthy adults. A short questionnaire in the app estimates your caffeine sensitivity and replaces the default with a personalised half-life, which then drives every chart, widget and forecast.
How long before bed should I stop drinking coffee?
Doppio starts from a caffeine-free window of about 6 hours before bedtime, based on research showing that caffeine taken 6 hours before bed still reduced sleep (Drake et al., 2013), and adjusts it between roughly 4 and 8 hours using your half-life, sensitivity and your own sleep data. The app turns this into a concrete last-coffee time and shows which drink you can still have.
What is the bedtime forecast?
It is your estimated caffeine level at the time you usually go to bed. Doppio compares it with a threshold that depends on your sensitivity: 35 mg for high sensitivity, 50 mg for normal and 65 mg for low. Bedtime comes from your Apple Health sleep data when available, with 23:00 as the fallback.
Can Doppio show how caffeine affects my sleep?
Yes. If you allow Apple Health sleep access, Doppio puts each night next to the previous day's caffeine and compares your sleep on high-caffeine and low-caffeine days. You can also rate how you felt each morning.
Is Doppio free?
Doppio is free to use for logging caffeine, the live level, the bedtime suggestion on Home, the last month of history, and the brew calculator and timer. Doppio Pro adds caffeine and sleep insights, full history, guided detox plans, more saved brews, the coffee shelf, extra themes and larger widgets. Pro is a yearly subscription or a one-time lifetime purchase, with prices shown in the App Store.
Which devices and languages does Doppio support?
Doppio runs on iPhone and iPad with iOS or iPadOS 18.0 or later. It is available in English, German, Spanish, French, Italian, Dutch, Portuguese, Japanese, Korean, Turkish and Serbian.
Does Doppio work with Apple Health?
Yes. Caffeine you log can be written to Apple Health, caffeine already in Health can be imported, and sleep data can be read for the sleep insights. Each connection is opt-in and can be switched off separately.
Where is my data stored?
Your caffeine log, coffee shelf and saved brews stay on your device and in your private iCloud. Anonymous usage analytics never include your caffeine logs, health samples or notes.
Is Doppio medical advice?
No. Caffeine figures are estimates from a standard half-life model adjusted by your answers during setup, not measurements from your body. Doppio is not a medical device and does not give medical advice.