When should your last cup land?
Caffeine has a half-life of roughly five to six hours in most healthy adults. That one number decides how much of your 3 PM cup is still working at bedtime. Pick your night, pick how caffeine treats you, and get the hour.
Your last full cup
2:30 PM
The math, in one paragraph
Half-life means half. A 200 mg mug at your cut-off still leaves about 100 mg working five to six hours later — and a quarter dose past midnight. Nothing here diagnoses your sleep; it is one published number applied to your own clock. The full picture, including why decaf is not zero, lives in our field note: The caffeine cut-off: when your last cup stops being your business.
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WELCOME15General information about caffeine, not medical advice; individual metabolism varies widely with genetics, medications and pregnancy. If sleep is a persistent problem, that conversation belongs with your doctor.