Starting from the current time, this shows wake-up options that land on the end of a 90-minute sleep cycle. Pick the one closest to when you actually need to be up.
It takes the current time, adds the minutes it usually takes you to fall asleep (around 15 for many people), and treats that as the moment you drift off. From there it stacks 90-minute sleep cycles and shows where 4, 5, and 6 cycles land.
Waking near the end of a cycle tends to feel easier than waking in the middle of deep sleep. Choose whichever option is closest to your real alarm.
A few minutes either way is fine. Aiming for the nearest cycle, rather than an exact figure, is the version of this that is easy to keep using.
The tool above reads your real clock and does the math for you, but if you only want a rough idea, this static table covers the most common late-night bedtimes (assuming about 15 minutes to fall asleep).
| Bedtime | 4.5h (3 cycles) | 6h (4 cycles) | 7.5h (5 cycles) | 9h (6 cycles) |
|---|---|---|---|---|
| 23:00 | 03:45 | 05:15 | 06:45 | 08:15 |
| 00:00 | 04:45 | 06:15 | 07:45 | 09:15 |
| 01:00 | 05:45 | 07:15 | 08:45 | 10:15 |
| 02:00 | 06:45 | 08:15 | 09:45 | 11:15 |
Four cycles (around 6 hours) is the realistic floor on a late night, and five cycles is the version that feels easiest on most mornings. 90 minutes is the average — individual cycles run roughly 80 to 110 minutes, and the first cycle of the night is often shorter than the later ones, so treat these times as targets, not exact figures. More on how sleep cycles actually work.
On a late night, deciding which cycle to wake on matters more than chasing an ideal amount of sleep. If you can still fit 6 hours (4 cycles), take that. If not, 4.5 hours (3 cycles) plus a short 15–20 minute nap early the next afternoon is usually easier to recover from than an odd cut in the middle of a cycle.
If the night is turning into an all-nighter — or already did — see how to recover from an all-nighter for getting through the next day.
If your alarm is fixed and you want to work backward to a bedtime instead, the sleep calculator does that.
Open the sleep calculatorIf you have been lying down for 20 minutes or more without drifting off, the calmer move is to get out of bed for a short while rather than pushing harder.
What to do when you cannot fall asleepIf 6 hours (4 cycles) still fits, that is the first choice. When it does not, cutting to 4.5 hours (3 cycles) so you wake at the end of a cycle, then adding a short 15–20 minute nap the next day, tends to feel easier than an in-between amount that lands mid-cycle.
This tool assumes night sleep. For daytime naps, keeping it to 15–20 minutes — short of a full cycle — is the length that avoids most of the post-nap grogginess (sleep inertia).
90 minutes is an average. Individual cycles run roughly 80 to 110 minutes, and the first cycle of the night is often shorter than the later ones. Treat the times shown as targets, not exact answers.
Yes. The tool counts cycles from the current moment rather than assuming a normal night, so daytime sleep works the same way. Darkening the room and keeping it quiet helps daytime cycles hold together.