Wake up refreshed,
not groggy.
Your brain cycles through 90-minute stages all night. Waking at the end of a cycle — not mid-deep-sleep — makes all the difference.
Wake-up time
Includes 14 min to fall asleep (Drake et al., 2013)
Go to sleep at…
Sleep right now
You fall asleep in ~14 min — we count that
Wake up at…
Each 90-min cycle shifts from physical repair (deep sleep N3, dominant in cycles 1–2) to emotional and memory processing (REM, dominant in cycles 4–6). Cutting your night short by 2 hours eliminates up to 70% of your REM sleep — disproportionately costly.
Source: National Academies / Institute of Medicine — Sleep Architecture Data
Your caffeine curfew
matters more than you think.
A coffee 6 hours before bed still costs you 41 minutes of sleep — even if you feel fine. Find your personal cut-off time.
Your drink
Type
Cups / servings
I drank it at
I plan to sleep at
Metabolism / sensitivity
Caffeine level through your day
400 mg of caffeine consumed 6 hours before bed reduced total sleep time by ~41 minutes in a double-blind study. Even the participants who felt they slept normally showed objective disruption.
Drake et al. (2013) — Journal of Clinical Sleep Medicine (PMID 24235903)
The right nap at the right time.
A 20-minute nap improves alertness. A 60-minute nap triggers deep sleep and grogginess. Science says timing and duration both matter.
Choose your nap type
I want to nap now (current time)
My bedtime tonight
NASA research (Rosekind et al., 1995) showed a ~40-min cockpit nap improved pilot performance by 34% and vigilance by 100%. The "coffee nap" beat both caffeine and napping alone in a separate study.
Hayashi et al. (2003) — Psychophysiology · NASA / Rosekind et al. (1995)
How much sleep do
you owe your brain?
Sleep debt accumulates silently. After 14 days of 6h/night, cognitive performance matches 2 full nights without sleep — and most people don't notice.
Hours slept this week
My nightly target:
hours
Enter 0 if you didn't sleep (all-nighter)
This week — day by day
After 14 days of 6h/night sleep restriction, cognitive deficits equal two full nights of total sleep deprivation. Critically, subjects self-rated their sleepiness as normal — they couldn't feel how impaired they were.
Van Dongen et al. (2003) — Sleep (PMID 12683469)