Sleep Cycle Calculator

Wake up refreshed. Based on 90-minute sleep cycles, this calculator shows the best times to go to bed or wake up so you never interrupt a sleep cycle.

Resultado instantâneo Funciona no navegador

Sleep cycles & quality

CyclesDurationQuality
4 cycles6 hoursMinimum — only for emergencies
5 cycles7.5 hoursGood — suitable for most adults
6 cycles9 hoursIdeal — full recovery

How it works

1 sleep cycle = 90 minutes
5–6 cycles (7.5–9 h) = optimal rest

The average sleep cycle lasts 90 minutes. Waking up mid-cycle causes grogginess (sleep inertia). Adding ~14 minutes accounts for the time it takes to fall asleep.

Como usar?

  1. 1
    Choose a tabPick 'When should I sleep?' if you know when you must wake up, or 'When should I wake up?' if you know your bedtime.
  2. 2
    Enter your timeType your target wake-up or bedtime. Adjust the fall-asleep time if yours differs from the 14-minute default.
  3. 3
    Pick a resultChoose a time marked 'Recommended' (5–6 cycles). These give the best balance of rest and waking up between cycles.

Perguntas frequentes

Why are sleep cycles 90 minutes?
A full sleep cycle moves through light sleep, deep sleep (slow-wave) and REM sleep. Research shows each cycle averages 90 minutes for adults, though it can range from 80 to 110 minutes. Completing full cycles reduces grogginess upon waking.
What happens if I wake up mid-cycle?
Waking during deep sleep or REM causes sleep inertia — the groggy, disoriented feeling that can last 15–60 minutes. By timing your alarm to land between cycles, you wake naturally during the lightest stage of sleep.
How many hours of sleep do adults need?
The CDC and most sleep researchers recommend 7–9 hours for adults (18–64). That corresponds to 5–6 full sleep cycles. Teenagers need 8–10 hours; older adults 7–8. Consistently sleeping fewer than 6 hours is linked to higher risk of cardiovascular disease, obesity and cognitive decline.

Why Sleep Cycles Matter

Sleep is not a single continuous state — it cycles through distinct stages every ~90 minutes: light sleep (N1, N2), deep slow-wave sleep (N3) and REM (dreaming). Each stage serves a different biological function: N3 repairs tissue and strengthens the immune system; REM consolidates memory and regulates mood.

The Science of Sleep Inertia

Sleep inertia — the groggy, impaired feeling after waking — is worst when you are roused from N3 (deep) sleep. It can impair performance for up to 30 minutes. Timing your alarm to fall between cycles minimises inertia and leaves you feeling genuinely rested.

Tips for Better Sleep

Keep a consistent sleep and wake time seven days a week — even on weekends. Avoid screens 30–60 minutes before bed (blue light suppresses melatonin). Keep your bedroom cool (16–19°C is optimal) and dark. Avoid caffeine after 2 pm; its half-life is 5–6 hours, meaning half the caffeine from a 3 pm coffee is still active at 8 pm.

Comentários