If I sleep now, when should I wake up?
The wake times below end at the boundary of a complete 90-minute sleep cycle, starting from right now. Set an alarm for one of them to wake up between cycles instead of in the middle of deep sleep.
Wake up at one of these times
includes ~14 min to fall asleepMinimum — expect grogginess
Acceptable on short nights
Recommended for most adults
Full restorative sleep
Pick a time at the start of a complete cycle to wake feeling rested, not groggy.
How to read this
Each option ends a whole 90-minute cycle. The optimal option (5 cycles, 7.5 hours) is where most adults wake refreshed with a full night behind them. The good option (6 cycles, 9 hours) is for recovering from a sleep deficit. The short options (3–4 cycles) work occasionally when the choice is between short sleep on-cycle versus longer sleep interrupted mid-cycle — the shorter cycle-aligned sleep usually feels better on waking.
The late-night decision
The most common reason people search “if I sleep now, when should I wake up” is that it’s late, they have somewhere to be in the morning, and the choice is between two imperfect options. The math above helps because it removes the false choice of “shall I sleep 5.5 hours or 6 hours” — neither of those lands at a cycle end. Waking at 5:47 AM after 5.5 hours in bed produces different sleep inertia than waking at 6:00 AM after 6 hours. Cycle-aligned wake times consistently beat the alarm-clock rounded ones.
When cycle math stops mattering
The 90-minute cycle is a population average. Your actual cycles run somewhere between 80 and 110 minutes, and they lengthen across the night. If your alarm still leaves you groggy after a full 5-cycle sleep, your personal cycle length probably isn’t 90 minutes. Try shifting your bedtime 15 minutes earlier or later for a week and see if wake grogginess improves — that’s the empirical way to find your rhythm without a sleep lab.
Questions
Why does the wake time change every time I open this?
Because it’s calculated from your current clock time. If you open the page at 11:03 PM, the wake times end at 6:33 AM, 8:03 AM, and so on. Open it again at 11:47 PM and everything shifts 44 minutes later. The math is anchored to now, not to a static example.
What if I can’t fall asleep in 14 minutes?
The wake times include a 14-minute buffer for typical sleep onset. If you know you take 25–30 minutes to fall asleep, add that time to the suggestions. If you’re falling asleep in under 10 minutes routinely, that’s often a sign of sleep deprivation worth taking seriously.
Is one more sleep cycle always better than waking earlier?
Yes, when the extra cycle fits your morning. Waking after 6 cycles (9 hours) leaves you rested but eats an extra 1.5 hours. Waking after 4 cycles (6 hours) works occasionally but not as a routine — chronic 6-hour sleep produces measurable cognitive costs after two weeks in controlled studies.
What if it’s already after midnight and my morning starts early?
You have two options: sleep for 3 cycles (4.5 hours) and accept some sleep debt, or sleep for 1 cycle (~90 minutes) and use morning bright light + caffeine to push through. Neither is sustainable — both are legitimate one-off tactics.