How the caffeine sleep calculator works
The decay curve at your bedside
Caffeine halves predictably: average ~5 hours, faster or slower by genetics and habits. The damage mode is not the dramatic all-nighter — it is the 40 mg still aboard at midnight, lengthening sleep onset, shaving deep sleep, and setting up tomorrow's 3 pm crash that invites the next afternoon dose. The loop is the product; the cutoff is the off-ramp.
Why "I sleep fine" is unreliable
Subjective sleep reports are notoriously poor instruments — people who fall asleep quickly report no effect while objective measures show reduced deep sleep and more awakenings. The honest test: two weeks with a 10-hour cutoff versus your usual, comparing morning alertness and afternoon energy. The data usually speaks plainly.
Working with the curve instead of against it
Morning doses are cheap (14+ hours to decay). Noon doses are moderate. Anything past 2 pm pays the half-life tax — switch to decaf (2–15 mg), tea varieties with lower caffeine, or the ritual without the molecule. Total daily dose still matters: ~400 mg is the adult ceiling, ~200 in pregnancy.