Caffeine Half-Life & Sleep Cutoff Calculator
Calculate residual caffeine milligrams remaining in your bloodstream at bedtime and determine your personal afternoon cutoff time to protect deep sleep.
Calculated Results
Frequently Asked Questions
What is the biological half-life of caffeine?
In healthy adults, caffeine has an average biological half-life of 5 hours (ranging from 3 to 7 hours depending on genetics, oral contraceptives, and liver enzyme CYP1A2 activity). This means 50% of the caffeine remains in your bloodstream 5 hours after drinking it, and 25% remains 10 hours later.
How does caffeine ruin sleep even if you can fall asleep easily?
Caffeine is an adenosine receptor antagonist. Even if you fall asleep, residual caffeine prevents the brain from entering restorative Stage 3 and 4 deep slow-wave sleep, reducing physical tissue repair, memory consolidation, and leaving you unrefreshed the next morning.
What is the recommended afternoon caffeine cutoff time?
Sleep researchers (including Dr. Matthew Walker and Dr. Andrew Huberman) universally recommend cutting off all caffeine consumption at least 8 to 10 hours before your target bedtime.
What accelerates or slows down caffeine metabolism?
Cigarette smoking accelerates caffeine clearance by 50%. Conversely, pregnancy and oral contraceptive pills double caffeine's half-life (up to 10-15 hours), making women on birth control far more sensitive to late-day caffeine.