Sleep Calculator – Best Time to Sleep or Wake Up

Find the best time to go to bed or wake up so you wake between 90-minute sleep cycles and feel fresher.

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    Sleep cycle calculator

    Ever slept eight hours and still woken up groggy? The timing may be the problem. Sleep runs in cycles of about90 minutes, and waking up mid-cycle — from deep sleep — leaves you foggy. This sleep calculator works backwards from your alarm to suggest bedtimes that let you wake between cycles, or forwards from your bedtime to suggest wake-up times. It allows time to fall asleep, and highlights the options that give a healthy 7½–9 hours.

    How to use it

    1. Choose whether you're planning your bedtime or your wake-up time.
    2. Enter the time (or tap “Going to bed now”).
    3. Pick one of the suggested times — five or six cycles is ideal for adults.

    Example

    To wake at 6:30 am, aim to be in bed by 9:15 pm (6 cycles, 9 hours of sleep) or10:45 pm (5 cycles, 7½ hours). If you go to bed at 11:00 pm, the best alarms are 6:45 am or 8:15 am. Pair good sleep with enough water and movement — see the water intake calculator and steps to km converter.

    Health disclaimer: This tool gives general estimates for information only and is not medical advice, diagnosis or treatment. Please consult a qualified doctor about your health. Read the full disclaimer.

    Frequently asked questions

    What is a sleep cycle?
    During the night you move through repeating cycles of light sleep, deep sleep and REM (dreaming) sleep, each lasting roughly 90 minutes. Waking at the end of a cycle, during light sleep, usually feels easier than being woken from deep sleep.
    How much sleep do I need?
    Most adults need 7–9 hours a night — about five or six cycles. Teenagers need 8–10 hours and school-age children 9–12. Regularly sleeping less than 6 hours is linked to poorer health and concentration.
    Why does the calculator add 15 minutes?
    Most people take 10–20 minutes to fall asleep. The calculator adds this so the cycles start when you actually fall asleep, not when you lie down. You can change it.
    Are cycles always exactly 90 minutes?
    No — they range from about 80 to 110 minutes and change through the night, so treat the times as a helpful guide. A consistent sleep and wake time every day matters even more.

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