Sleep Need Calculator
Calculate your optimal sleep duration and ideal bedtime to wake up refreshed, based on sleep science.
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Frequently Asked Questions
How much sleep do I really need?
Adults need 7–9 hours, but the optimal amount varies by age, activity level, and genetics. Athletes and very active people often need 8–9.5 hours. The key is not just duration but timing — aligning with your natural sleep cycles.
What is a sleep cycle and why does it matter?
A sleep cycle lasts approximately 90–95 minutes and includes light sleep, deep sleep, and REM stages. Waking at the end of a cycle (rather than mid-cycle) makes you feel more refreshed. That’s why 7.5 hours can feel better than 8.
Does chronotype affect how much sleep I need?
Your chronotype (early bird vs. night owl) affects your optimal sleep timing, not necessarily duration. Night owls forced to wake early accumulate sleep debt. Aligning your schedule with your chronotype improves sleep quality significantly.
What happens if I consistently sleep less than 7 hours?
Chronic sleep deprivation increases risk of cardiovascular disease, weakens immunity, impairs cognitive function, and accelerates biological aging. Even 1 hour less per night compounds into measurable health effects within weeks.
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References
- • Hirshkowitz M et al. (2015). “National Sleep Foundation's sleep duration recommendations.” Sleep Health, 1(1):40-43.
- • Mah CD et al. (2011). “The effects of sleep extension on athletic performance.” Sleep, 34(7):943-950.
- • Léger D et al. (2023). “Sleep cycle duration variability.” Sleep Medicine Reviews.
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