SleepCycleCalcIf I Go to Sleep Now, When Should I Wake Up?
It is late, or you are exhausted, and the decision is already made: you are going to sleep now. The only question left is the alarm. This tool reads the current time on your device and counts forward in full 90-minute cycles.
Calculated from the current time on your device, plus your fall-asleep buffer, in full 90-minute cycles.
Reading the options
The list runs from 3 cycles (4½ hours) to 6 cycles (9 hours). Take the longest your morning honestly allows — but set the alarm for one of these times rather than a round number in between. Waking 30 minutes later, mid-cycle, can genuinely feel worse than waking at the earlier boundary, which is a strange but well-known quirk of sleep inertia.
One practical tip for very short nights: put the alarm across the room and get light — daylight or a bright lamp — as soon as you are up. Light is the strongest signal that tells your body clock the night is over, and it shortens the groggy window more than snoozing does.
Frequently asked questions
If I go to sleep now, when should I wake up?
That is exactly what this page calculates, from the clock on your device: it adds your fall-asleep buffer, then offers wake times at the end of 3, 4, 5 and 6 full 90-minute cycles. Pick the latest one your morning allows.
I have to be up in 4 hours. Is it worth sleeping at all?
Almost always yes. Around 4 hours covers roughly 2½–3 cycles, including most of the night's deep sleep, and performs noticeably better than staying up all night. Set the alarm at a cycle boundary if you can, keep the room dark, and plan a slow start — you will still carry sleep inertia and a debt to repay the next night.
Should I use this before an early flight or exam?
Yes — it is the classic use case. Anchor on the wake time you cannot move, and if none of the full-night options fit, a 90-minute or 20-minute nap timed with our nap calculator is a better plan than unplanned dozing.