How much sleep did I get?
Enter the time you fell asleep and the time you woke up. The calculator shows how long you actually slept, how many full 90-minute cycles that works out to, and how it compares to a healthy night.
What counts as enough?
Most adults need 7 to 9 hours a night, which is roughly 5 to 6 full sleep cycles. Because each cycle averages 90 minutes, the cleanest targets are 7.5 hours (5 cycles) or 9 hours (6 cycles) — waking at the end of a cycle leaves you alert, while waking mid-cycle causes the groggy feeling known as sleep inertia.
This tool measures time asleep, not time in bed. If you lay down at 11 PM but didn’t actually drift off until 11:25, enter the later time for an honest number. Most people spend 15–20 minutes falling asleep and a little time awake during the night, so time in bed is usually 20–40 minutes longer than time asleep.
Plan a better night
Want to wake up at the end of a cycle next time? Use the sleep cycle calculator to find the ideal bedtime for your alarm, or check your accumulated sleep debt across the week.