What a cycle boundary is, arithmetically
A boundary on this site is a multiple of a number you set. That is a smaller thing than it sounds, and it is worth being exact about how much smaller.
When a page says a bedtime gives you five whole cycles, it means the interval between the assumed moment of falling asleep and the alarm divides by the assumed cycle length with nothing left over. Both of those are assumptions. The boundary is a property of the sum, not something the site has observed happening in you.
Three things it does not mean
- It does not mean your cycles actually ended there. Real intervals vary between people and drift across a night, so a boundary predicted eight hours in advance from a fixed average is, at best, approximate.
- It does not mean that waking anywhere else is harmful. This site has no findings about that and makes no claim about it in either direction.
- It does not mean the shortest option on a table is sufficient. Three cycles is four and a half hours and the page will print it, because you asked what three cycles comes to, not whether three is enough.
What it does mean
That if you accept the two assumptions, the arithmetic is right. Every sleep table on this site is conditional in that way, and printing both conditions on every page is the only honest way to offer the result at all.
If the question you actually have is about sleeping badly, waking repeatedly, or being tired in a way that a bedtime does not explain, that is a question for a doctor. It is not a question a page of subtraction can take.
The full list of what this page cannot see is set out in what this site cannot know.