Last updated: October 2026
What time should I go to bed to wake up at 7am?
Short answer: to wake up at 7:00 AM feeling rested, go to bed at 9:45 PM for 6 full sleep cycles (9 hours) or 11:15 PM for 5 cycles (7.5 hours). These times include ~15 minutes to fall asleep, so they count from lights-off in bed. Enter your own wake-up time in the calculator above for exact bedtimes.
The 90-minute sleep cycle
Your brain doesn't sleep in one flat block — it cycles through light sleep, deep sleep and REM roughly every 90 minutes. Waking at the end of a cycle, during light sleep, feels easy; waking from deep sleep mid-cycle is what causes that heavy alarm-clock fog. Learn more on Wikipedia's sleep cycle overview.
That's why total hours alone don't predict how refreshed you'll feel. Sleeping 6 complete cycles (9 hours) or 5 cycles (7.5 hours) beats sleeping 8 hours that chop a cycle in half.
Most adults feel best with 5–6 full cycles. The calculator adds a 15-minute fall-asleep buffer to every result — if you usually drift off faster or slower, nudge your bedtime by a few minutes.
How to use the calculator
1. Choose a mode: I wake up at if your alarm time is fixed, or I go to bed at to see when you'll naturally wake. 2. Enter the time — in bed mode you can tap Use now to fill in the current time. 3. Pick a bedtime (or wake-up time) that gives you 5–6 complete cycles and matches your schedule.
Frequently asked questions
Why are sleep cycles 90 minutes?
Most people cycle through the stages of sleep — light, deep and REM — about every 90 minutes. Waking up at the end of a cycle, when you're in light sleep, feels far easier than being jolted out of deep sleep mid-cycle. That's why this calculator steps in 90-minute blocks.
How many sleep cycles do I need per night?
Aim for 5 to 6 full cycles, which is 7.5 to 9 hours of actual sleep. Most adults do well on 5 cycles; teenagers and people recovering from illness often need 6. Fewer than 3 cycles (under 4.5 hours) isn't enough for healthy functioning.
What happens if I wake up in the middle of a sleep cycle?
Waking from deep sleep mid-cycle usually means grogginess and disorientation — the classic alarm-clock fog. If you have to wake at a fixed time, it can feel better to aim for 5 complete cycles than to squeeze in 6 hours that cut a cycle short.
Does the 15-minute fall-asleep buffer matter?
Yes — most people take around 15 minutes to drift off, and the calculator subtracts (or adds) that time so the cycles start when you're actually asleep. If you usually fall asleep faster or slower, adjust your bedtime by a few minutes.
Is my sleep data private?
Completely. Every calculation runs locally in your browser with JavaScript — nothing you enter is sent to a server, stored, or tracked.
