Question 1

How does the sleep calculator work?

Accepted Answer

Our sleep calculator uses the science of 90-minute sleep cycles. Each cycle moves through four stages: N1 (light), N2 (core), N3 (deep slow-wave), and REM (dream sleep). We add 14 minutes — the average time adults take to fall asleep — then calculate times that place your alarm at the natural end of a cycle, during light sleep.

Question 2

What time should I go to sleep if I wake at 6am or 7am?

Accepted Answer

For a 6:00 AM wake time, your optimal bedtimes are: 9:16 PM (6 cycles), 10:46 PM (5 cycles — recommended), or 12:16 AM (4 cycles). For a 7:00 AM wake time: 9:46 PM (6 cycles), 11:16 PM (5 cycles, recommended), or 12:46 AM (4 cycles).

Question 3

Why 90 minutes for a sleep cycle?

Accepted Answer

Sleep cycles averaging 90 minutes were first documented by sleep researcher Nathaniel Kleitman in 1953. While individual cycles range from 70 to 120 minutes, 90 minutes is the evidence-based population average used by sleep scientists worldwide.

Question 4

Can shift workers use this calculator?

Accepted Answer

Yes. Simply enter the time you need to wake up — regardless of whether it is morning, afternoon or evening — and the calculator finds your optimal sleep time based on 90-minute cycles.

Question 5

How accurate is this calculator?

Accepted Answer

The calculator uses the same 90-minute cycle model used in clinical sleep science. Individual cycles vary between 70 and 120 minutes. If you consistently feel groggy at the recommended times, adjust your bedtime by 15 minutes earlier or later.

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