CaffSenseHow long does caffeine stay in your system?
Tap your drinks. Watch the curve. See what's left at bedtime.
Everyone metabolizes caffeine differently — roughly 2–8 h (EFSA 2015).
From a tap to your own pattern
Log in seconds
Tap coffee, espresso, black or green tea, cola, an energy drink or energy shot — from your iPhone, Apple Watch, or a widget.
See your live curve
Watch caffeine rise and fall through your day and see how much is still active at your bedtime.
After 7 nights
CaffSense surfaces your personal pattern from your logged caffeine and Apple Health sleep — your sleep threshold, caffeine–sleep insights, even an overnight heart-rate & HRV signal.
A look inside the app
Dark, focused, and built around one number: how much caffeine is still in you.
Everything CaffSense does
One-tap logging
Coffee, espresso, black & green tea, cola, energy drinks & energy shots — from iPhone, Apple Watch or a widget.
Live half-life curve
Watch caffeine rise and fall through your day and see what's still active at bedtime.
Personal cutoff
After ~7 nights, CaffSense learns your sleep threshold and tells you when to stop.
Caffeine–sleep insightsPro
Connects your caffeine timing to your own Apple Health sleep — incl. an overnight heart-rate & HRV signal.
“What-if” plannerPro
See a coffee's bedtime impact before you drink it.
Trends & streaksPro
Your typical day, weekly trends and a clean-night streak.
Guided reductionPro
A gentle, step-by-step mode to cut back at your own pace.
Widgets & Live Activity
Cutoff countdown on your Lock Screen and in Dynamic Island, plus an Apple Watch complication.
100% on device
No account, no server, works offline. Available in English, German & French.
No promises. Your data.
Most trackers stop at logging. CaffSense looks for an association between when you have caffeine and how you actually sleep — and always shows how many nights it is based on.
Your data shows: nights with caffeine after 2:00 pm had −24 min deep sleep on average vs. your baseline (n=12).
Patterns are observational and may be affected by stress, alcohol, exercise, illness, medication, and data quality.
Illustrative example of an in-app insight. Your real insights are built only from your own logged data.
Built for privacy
- No account, ever
- Your caffeine & Health data stay on your iPhone
- Works offline
No ads, no cross-app tracking. Only anonymous, aggregated paywall analytics — opt out anytime in the app.
The science, briefly
Caffeine clears on a half-life: every few hours, about half of what's active is gone. The exact rate is personal — which is why CaffSense learns yours instead of assuming. The curve above uses a first-order decay model with an adjustable 2–8 h half-life.
- EFSA (2015) — Scientific Opinion on the safety of caffeine: half-life ~2–8 h.
- Drake et al. (2013) — Caffeine taken 0/3/6 h before bed and its effect on sleep.
- FDA — Consumer guidance on caffeine (≈400 mg/day for healthy adults).
Insights are based on your own logged caffeine and available Apple Health sleep data. They are observational wellness information only, not medical advice, and they should not be used to diagnose, treat, cure, or prevent any condition.
Free to start. Pro when you want the pattern.
Free
- Caffeine logging
- Live half-life curve
- 3-day history
Pro
- Your personal sleep threshold — from your own nights
- Caffeine–sleep insights, incl. overnight heart-rate & HRV signal
- “What-if” planner — a coffee’s bedtime impact before you drink it
- Your typical day, weekly trends & clean-night streak
- Guided gradual reduction mode
- Live Activity countdown + Apple Watch complication
- Full history
Prices shown are launch pricing (as of 2026-06) and may change.
Questions
Is this medical advice?
No. CaffSense provides general wellness information based on your logged caffeine and available Apple Health sleep data. It is observational and does not diagnose, treat, cure, or prevent any condition.
Where is my data stored?
On your device. There is no account and no server backend — your caffeine logs, calculations, and insights stay on your iPhone.
Do I need an Apple Watch?
No. An Apple Watch makes one-tap logging easier, but it isn't required. CaffSense works on iPhone alone.
How accurate is the half-life?
Caffeine half-life varies between people — roughly 2 to 8 hours (EFSA 2015). CaffSense uses a 4-hour default you can adjust, which is exactly why the app personalizes your cutoff from your own data over time.
How does it use Apple Health?
With your permission, it reads sleep data from Apple Health to build your baseline and can save caffeine entries you create. You can change permissions any time in the Health app.
What's free and what's Pro?
Logging, the live curve, and a 3-day history are free. Pro ($9.99/year or $1.99/month, 7-day free trial) adds your personal sleep threshold, caffeine–sleep insights (incl. an overnight heart-rate & HRV signal), a “what-if” planner, your typical day, weekly trends & streaks, a guided gradual reduction mode, a Live Activity cutoff countdown, an Apple Watch complication, and full history.
How do I cancel the trial?
Cancel any time in your Apple subscription settings before the 7-day trial ends and you won't be charged.
Does the website track me?
No cookies, no third-party trackers. We use privacy-friendly, cookieless analytics (GoatCounter) for aggregate page counts only.
Caffeine & sleep guides
How long does caffeine stay in your system?
Half-life explained, drink-by-drink, plus what makes it last longer for you.
When to stop drinking coffee before bed
The 6–10 hour guidance and how to find your personal cutoff.
Caffeine & sleep
How leftover caffeine cuts deep sleep — and how to spot your own pattern.
Caffeine in coffee, tea & energy drinks
A milligram comparison chart for everyday drinks.
Best time to drink coffee
Your ideal coffee window — and the cutoff that protects sleep.
Why am I tired after coffee?
The adenosine rebound behind the afternoon crash.
How much caffeine is too much?
Safe daily limits (~400 mg) and the exceptions.