act now · 9 calculators
Tonight
Everything with a time attached to it tonight: when to go to bed, the last coffee, the last drink, screens down, and lights out.
- Sleep Timing
When to go to bed and when to wake, aimed at 90-minute cycle boundaries so the alarm lands between cycles.
- Nap
The right nap length for your goal, alertness, memory, or recovery, and the latest time to take it.
- Caffeine
The latest safe coffee for your bedtime, and how much of what you already drank is still in your system.
- Alcohol
How tonight's drinks change tonight's sleep, REM loss, wake-ups, and when the last drink should end.
- Wind-down
Screens down and the body's own melatonin window, timed back from your target bedtime.
Read the science
Sleep Cycles Explained
What happens during a 90-minute sleep cycle, why each stage matters, and how to wake up without feeling wrecked.
Caffeine and Sleep: Half-Life, Adenosine, and Your Cutoff Time
How caffeine works in the brain, why its half-life matters more than how you feel, and the research on its real impact on sleep architecture.
Why 90-Minute Cycles Matter
Sleep cycles are 90 minutes for a reason. The research behind the cycle, why timing wake-ups to cycle ends reduces sleep inertia, and how individual cycle length varies from 80 to 110 minutes.
Educational information, not medical advice. Consult a healthcare provider for sleep disorders or before taking any supplement.