Caffeine, sleep, and timing
Track how caffeine may interact with your sleep
Caffeine can fade as a feeling before it has fully cleared. SlumberBrew helps you see the estimated amount still in your system at bedtime, so you can decide what your next drink means for your night.
Open the free caffeine tracker
What SlumberBrew tracks
Log coffee, tea, energy drinks, or a home brew and the tracker estimates your caffeine level now, what may remain at bedtime, and when it is likely to drop back under the bedtime target you chose. It is about timing as well as totals: two drinks with the same milligrams can leave different amounts at bedtime depending on when you had them.
Why caffeine can still matter after the boost fades
The body clears caffeine gradually. A half-life is the time it takes for roughly half of the amount in your system to clear. That means the noticeable lift can be gone while a smaller amount is still present. The tracker shows that gradual tail instead of treating caffeine as either fully active or completely gone.
The result is an estimate, not a reading from your body. Coffee strength, serving size, metabolism, medication, pregnancy, and other factors can change the real result.
Why the result is personal
People clear caffeine at different rates. SlumberBrew gives you a half-life setting so the estimate can reflect a faster or slower pattern rather than assuming everyone processes caffeine identically. The brew calculator also gives a range because the same named drink can vary considerably between cafés and kitchens.
Browser tracker or iPhone app?
The browser tracker keeps your drink log in your browser and compares it with the bedtime target you set. It does not read your health data. The iPhone app can optionally connect Apple Health so you can look at your caffeine pattern alongside sleep recorded on your phone or watch.
How to use the tracker
- Set your bedtime, wake time, and preferred bedtime target.
- Choose the drink you had, or use the brew calculator for coffee you made yourself.
- Check what may remain at bedtime before deciding whether to have another.
- Adjust the metabolism setting if the default estimate does not describe your usual experience.
Sources and limitations
SlumberBrew's model is based on published work about caffeine half-life, absorption, variation between people, and sleep. The homepage lists the source papers, including Blanchard and Sawers, Nehlig, and Drake and colleagues.
SlumberBrew is not a medical device and none of its estimates are medical advice. If you have a health condition, take medication, are pregnant, or are worried about caffeine or your sleep, talk to a doctor.
How long does caffeine stay in your system? · How much caffeine is in coffee? · How much caffeine should you have? · Read the science and method · Use the caffeine cutoff calculator · Read more support questions