If you go to bed now
The clock below starts at the time it is where you are. Each line is a whole number of cycles from the moment you are assumed to be asleep, which is a few minutes after you get in.
Wake at 6:45 am
5 cycles and 7h 30m asleep: the row nearest eight hours.
| Wake at | Cycles | Time asleep |
|---|---|---|
| 12:45 am | 1 cycle | 1h 30m |
| 2:15 am | 2 cycles | 3h |
| 3:45 am | 3 cycles | 4h 30m |
| 5:15 am | 4 cycles | 6h |
| 6:45 am | 5 cycles | 7h 30m |
| 8:15 am | 6 cycles | 9h |
7h 30m asleep
The night nearest eight hours from the time in the field above.
The two assumptions
Move either one and every time above moves with it. The settings follow you around the site.
Reading the table
The shortest line is at the top, so the table reads from the earliest alarm that ends a whole cycle to the latest. Every line is a full cycle: the arithmetic has no opinion about the ones near the top, it just counts them.
The time in the field is your device's clock, and it moves on its own until you type over it. Type a time and it stays where you put it.
Two numbers do all the work here: the length of a cycle and the minutes between getting into bed and being asleep. The second matters more on this page than anywhere else on the site, because every wake time here is counted from the moment you are taken to be asleep.
The other direction
If the alarm is already fixed and the bedtime is the unknown, that is the same sum run backwards. There is a page for every wake time on the dial.
Shorter than a night
Under about three hours this stops being a night and starts being a nap, which is counted differently and has its own pages.