Sleep Calculator
Hours slept, and bedtimes that fit your sleep cycles
How long did I sleep?
7.5 hours — within the 7–9 hours most adults need
Overnight is handled automatically — 11:00 PM to 6:30 AM counts as 7h 30m.
Sleep cycle planner
Go to bed at one of these times:
- 6 cycles · 9h 0mRecommended
- 5 cycles · 7h 30mRecommended
- 4 cycles · 6h 0m
- 3 cycles · 4h 30m
Based on ~90-minute sleep cycles plus 15 minutes to fall asleep. Waking at the end of a cycle tends to feel easier than mid-cycle.
How the sleep cycle math works
Sleep isn't one continuous state — it runs in cycles of light sleep, deep sleep, and REM that average roughly 90 minutes each. Waking at a cycle boundary usually feels easier than being pulled out of deep sleep mid-cycle, even with slightly less total sleep. The planner works backward from your wake-up time in 90-minute steps and adds about 15 minutes for falling asleep.
Worked example: waking at 6:30 AM with six cycles means 6 × 90 + 15 = 555 minutes — bed at 9:15 PM. Five cycles puts bedtime at 10:45 PM for 7.5 hours of sleep, still inside the 7–9 hours most adults need.
Frequently asked questions
How many hours of sleep did I get?
Enter the time you went to bed and the time you woke up — the calculator handles overnight automatically, so 11:00 PM to 6:30 AM correctly reads 7 hours 30 minutes, shown in hours-and-minutes and decimal form.
What is a sleep cycle?
Sleep moves through light, deep, and REM stages in cycles averaging roughly 90 minutes. Waking at the end of a cycle tends to feel easier than being pulled out mid-cycle, which is why the planner suggests bedtimes in 90-minute steps rather than round hours.
What time should I go to bed if I wake at 6:30 AM?
For six full cycles (about 9 hours of sleep) go to bed around 9:15 PM; for five cycles (7.5 hours) around 10:45 PM. Both include roughly 15 minutes to fall asleep. The planner computes this for any wake-up time.
How much sleep do adults need?
Major sleep-health bodies recommend 7–9 hours per night for most adults, with individual needs varying. The calculator flags whether your night fell inside or outside that range.
Is this medical advice?
No — cycle lengths and sleep-need ranges are population averages, and your own rhythm may differ. If you have ongoing sleep problems, talk to a doctor or sleep specialist.
Related tools and guides
- Sleep hours guide — tracking your sleep patterns and what they mean
- Time duration calculator — the exact time between any two times
- Countdown timer — count down to your alarm, or anything else