When should I have my last coffee?
Work backwards from bedtime so that, on a simple sketch, about 25 mg or less may still be around when you get into bed.
The Sleep Reset program tests one change like this each week.
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How this works
Caffeine fades slowly. A common sketch uses a half-life of about 5 hours for a typical adult, about 3 hours if you clear it fast, and about 8 hours if you are sensitive. This tool asks: when is the latest you could have one usual drink so that roughly 25 mg or less may still be active at bedtime?
Twenty-five milligrams is about a quarter of a typical mug of brewed coffee. It is a conservative starting point, not a proven safe line. The three columns show how much the answer moves if your half-life is shorter or longer than typical.
The model is the same simple one used in the caffeine experiment: a short rise, then a slow fade. Brand, size, genetics, pregnancy, some medicines and smoking all change the real picture. If a week of an earlier last drink changes nothing, caffeine may not be your main lever.
Questions people ask
- Why 25 mg at bedtime?
- It is a small remainder — about a quarter of a typical mug — used here as a conservative starting point. It is not a medical limit.
- Does this replace the caffeine experiment?
- No. This gives one last-drink time. The experiment lets you log several drinks and see an estimated curve through the evening.
- What if I drink chai or tea, not coffee?
- Pick the matching drink. Chai and tea still carry caffeine, usually less than a mug of coffee, so the cutoff is often later.
This tool is educational, not medical advice, diagnosis or treatment. Persistent or severe sleep problems deserve a qualified medical assessment.