Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles to wake up feeling refreshed.
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Important Disclaimer
This calculator provides estimates for educational purposes only. Results are not a substitute for professional medical or nutritional advice. Always consult a qualified healthcare provider before making significant changes to your diet or exercise routine.
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Frequently Asked Questions About Sleep
What time should I go to bed to wake up refreshed?+
Sleep runs in cycles of about 90 minutes. Waking at the end of a cycle — rather than in the middle of deep sleep — helps you feel less groggy. Count back 5 or 6 cycles (7.5 or 9 hours) from your wake-up time, plus about 15 minutes to fall asleep.
How much sleep do adults need?+
Adults aged 18–64 need 7–9 hours of sleep per night; adults over 65 need 7–8 hours. Teenagers need 8–10 hours. Consistently sleeping less than 7 hours is linked with weight gain, poorer recovery and lower performance.
How long is one sleep cycle?+
A sleep cycle lasts roughly 90 minutes (between 70 and 120 minutes) and moves through light sleep, deep sleep and REM sleep. Most people go through 4–6 cycles per night.
Does sleep affect weight loss and muscle gain?+
Yes. Poor sleep increases hunger hormones, cravings and muscle loss during dieting, and reduces recovery from training. Getting 7–9 hours is one of the easiest ways to improve fat loss and muscle-building results.