A 30-minute nap
Thirty minutes is a third of a cycle, and the last length that still finishes before one would have.
| Stage | Time |
|---|---|
| 2:00 pm | you lie down |
| 2:15 pm | asleep, give or take |
| 2:45 pm | the alarm goes |
That is 45m of lying down for 30m of sleep, allowing 15 minutes to drop off.
The four lengths from the same moment
| Nap | Up at | Lying down for |
|---|---|---|
| 20 minutes | 2:35 pm | 35m |
| 30 minutes | 2:45 pm | 45m |
| 60 minutes | 3:15 pm | 1h 15m |
| 90 minutes | 3:45 pm | 1h 45m |
What the length is
A third of ninety is thirty exactly, which makes this the tidiest number on the page and means nothing at all: a cycle is not divided into thirds by anything, and being a neat fraction of an average is not a property of your afternoon.
Set against twenty minutes, this adds ten. Set against sixty, it saves half an hour. The table above is the whole of what this site can tell you about the difference, because the rest of the difference is about you and nobody here has measured it.
A nap is counted straight, not in cycles. The only assumption borrowed from the rest of the site is how long it takes you to fall asleep, and it is the same number you set on a wake page. Nothing here says a nap of any length will do anything for you.
Against the break rules
Thirty minutes asleep is forty-five lying down at the default drop-off. That is more than twice the United Kingdom's twenty-minute rest break. It is also fifteen minutes over the shortest meal interval a written agreement can set in South Africa, which is thirty minutes. The full hour the Basic Conditions of Employment Act gives most employees after more than five hours' continuous work takes it with a quarter of an hour left. United States federal law requires no lunch or coffee break. A break of five to twenty minutes that an employer does give counts there as paid work time.
The other three
A whole night instead
Past about three hours a nap is a short night, and short nights are counted in cycles on the wake-time pages, one for every quarter hour of the day.