When should my last coffee be?
Say when you plan to sleep next. The cutoff is worked backward from caffeine's half-life.
Updated August 2026
Enter a sleep time above to see your cutoff.
This is one number. The full plan is the whole day.
The free plan computes this cutoff plus light exposure, meal timing, wind-down, and naps around your actual shifts, not just one input.
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Common questions
Why 8 hours before bed?
Caffeine has a half-life of roughly five hours, meaning half of it is still in your system five hours after you drink it. Cutting it off eight hours before your target sleep time leaves only a small fraction on board when you lie down, low enough for most people to fall asleep without a fight.
Does working nights change the math?
No. The cutoff is always eight hours before whenever you actually plan to sleep, whether that's 11 PM or 9 AM after a night shift. Working nights changes what the clock says, not the rule.
When should my first cup be?
Wait 60 to 90 minutes after waking. Cortisol is already elevated right when you wake up, so an immediate cup does less for you than one taken after that window, once your natural alertness has started to dip.