Sleep Calculator

What do you want to work out?

Wake-up timeUsed by the wake-time and routine modes. Accepts 07:00 or 7:00 am.

Time you get into bedUsed when you are going to bed at a set time.

Target sleep length (hours)Routine mode only: the engine rounds this to the nearest whole number of cycles.

Sleep cycle length (min)The textbook average is about 90 minutes, with a normal range of roughly 90 to 110.

Time it takes you to fall asleep (min)Added to the time in bed. A sleep latency of 15 minutes or less is considered normal.

Age (years)Sets which recommended sleep duration the options are checked against.

Most cycles to show

Fewest cycles to show

Wind-down before bed (min)How long before getting into bed you stop screens, work and bright light.

Recommended time

23:15

Sleep Calculator

Recommended time (12-hour clock)

11:15 pm

Cycles in that option

Sleep in that option

7.50 hours

Get into bed at

23:15

Wake at

07:00

Start winding down at

22:45

Time in bed

7.75 hours

Options shown

Recommended sleep, lower

7.0 hours

Recommended sleep, upper

9.0 hours

Age band used

Adults 18 and over

Recommended option is within the guideline

yes

Worked out from Carskadon MA & Dement WC, Normal Human Sleep: An Overview, in Kryger, Roth & Dement (eds), Principles and Practice of Sleep Medicine, Elsevier and 3 other sources.

The 90-minute cycle is a population average. Individual cycles run roughly 90 to 110 minutes and lengthen through the night, so treat these times as a starting schedule to adjust, not a target to hit exactly.

Sleep-cycle timing is a scheduling convenience, not a treatment. Cycle length varies between people and across the night, and waking "between cycles" has not been shown to change daytime alertness on its own. Persistent trouble falling asleep, staying asleep, loud snoring, or sleepiness despite adequate time in bed should be assessed by a clinician rather than rescheduled.

How this is worked out

6 steps

Sleep cycle length 90 minutes, sleep-onset allowance 15 minutes.
6 cycles = 6 x 90 = 540 min asleep (9 h): bed 21:45, wake 07:00.
5 cycles = 5 x 90 = 450 min asleep (7.5 h): bed 23:15, wake 07:00.
4 cycles = 4 x 90 = 360 min asleep (6 h): bed 00:45, wake 07:00.
3 cycles = 3 x 90 = 270 min asleep (4.5 h): bed 02:15, wake 07:00.
Adults 18 and over: 7-9 hours per 24 h. Watson NF et al., Sleep 2015;38:843-844: adults should sleep 7 or more hours per night.

All cycle-aligned optionstable

cycles	bedTime	wakeTime	sleepHours	timeInBedHours
6	21:45	07:00	9	9.25
5	23:15	07:00	7.5	7.75
4	00:45	07:00	6	6.25
3	02:15	07:00	4.5	4.75

Results are general information, not financial, tax, legal, medical or engineering advice.