How to Use This Calculator
Choose whether you want to enter the time you need to wake up, or the time you're going to bed right now. Adjust the fall-asleep buffer if you know your own sleep latency, and the table instantly shows every bedtime or wake-up option in complete 90-minute cycles — 3 through 6 — so you can pick the one that fits your schedule while still landing at the end of a cycle. For the full explanation of sleep-cycle science, why waking mid-cycle causes grogginess, and a worked example for every number on this page, see the "How to Use the Sleep Cycle Calculator" section of our complete guide.
Read the full guide first for the best context: what actually happens in a 90-minute sleep cycle, how many cycles adults, teens, and children need, why "sleep debt" can't simply be repaid on the weekend, and a detailed worked example for every calculation on this page are all covered in our Sleep Cycle Calculator Guide 2026 →
This calculator provides general estimates for informational and educational purposes only. It is not medical advice. Sleep cycle length varies between individuals and across the night, and 90 minutes is a population average, not an exact personal figure. If you struggle with chronic insomnia, excessive daytime sleepiness, or suspect a sleep disorder such as sleep apnea, consult a doctor or sleep specialist.