The Caffeine Cutoff Calculator: When to Drink Your Last Coffee
How Caffeine Hijacks Sleep
It blocks adenosine receptors for 6-8 hours, delaying deep sleep onset by 40 minutes even if you fall asleep (Journal of Clinical Sleep Medicine).
The Genetic Factor
Slow metabolizers (CYP1A2 gene variant) feel caffeine’s effects 4x longer. 23andMe can test your sensitivity.
Half-Life Formula:
Body weight (kg) x 0.5 = hours to metabolize 50% of caffeine. A 150lb person needs ~7 hours.
Why Your 2PM Latte Keeps You Up
Personalized Cutoff Times
Early Birds vs Night Owls
Morning types should stop by noon; evening types may tolerate until 3PM without sleep disruption.
Decaf Alternatives:
Try chicory root or mushroom coffee after cutoff – provides ritual without sleep-stealing caffeine.