- The 90-minute sleep cycle is only an average — finding your ownFirst cycle 70–100 min · later ones longer · adjust the length
- 20-minute vs 90-minute naps and sleep inertia15–30 min short nap · one 90-min cycle · skip the hour
- Bedtime before an exam or an early flightCount back from wake-up · add time for nerves · start days ahead
- How to plan a sleep schedule for night and rotating shiftsMain sleep after work · short pre-shift nap · keep it dark
- Jet lag sleep plan — shifting your bedtime before a tripEast 1 h/day · West 1.5 h/day · shift 2–3 days ahead
- Kids’ recommended sleep by age and how to set their bedtimeAASM hours by age · count back from wake-up · teens 8–10 h
- Weekend catch-up sleep, sleep debt and social jet lagWhat the NIH study found · mid-sleep difference · extra sleep doesn’t cancel debt
- Snooze vs multiple alarms — setting a better morning alarm2023 snooze study · last alarm at a cycle end · one backup
- Caffeine cutoff time — how many hours before bed to stopHalf-life 3–5 h · 6 hours before bed still costs an hour · 8-hour cutoff
- How to reset your sleep schedule after the holidaysWake time first · 30–60 min a day · bedtime regularity score
Sleep Calculator
No sign-up, and your sleep log stays on your phone. Free on Android.