Sleep & Bedtime Calculator
How does your sleep schedule impact your health? Assess your nightly hours and bedtime to see estimated cardiovascular risk changes based on scientific data.
Size My Sleep & Bedtime
Your Habit Scale
| Assessment | Combined cardiovascular disease (CVD) Risk |
|---|---|
| Your Profile | 0% |
How It's Calculated
Your sleep-related cardiovascular disease (CVD) risk is estimated by comparing your habits to optimal patterns (7-8 hours sleep, 10-11 PM bedtime), which have a combined risk multiplier of 1.0.
- Your selected sleep duration (7-8 hours (Optimal)) has a CVD risk multiplier of 1.00.
- Your selected bedtime (10:00 PM - 10:59 PM (Optimal)) has a CVD risk multiplier of 1.00.
- The Combined cardiovascular disease (CVD) Risk is calculated as: (Duration Multiplier × Bedtime Multiplier). In your case: 1.00 × 1.00 = 1.00.
- This represents a 0.0% increase in relative CVD risk compared to someone with optimal sleep duration and bedtime.
Note: These multipliers are based on population studies and represent relative risk changes. '1.0' is the baseline for optimal sleep. Values >1.0 indicate increased risk, <1.0 (not applicable here) would indicate decreased risk.
Why It's Important
Getting 7–8 hours of sleep and lights-out around 10 PM is more than a “good night”—it’s your body’s best defense against disease.
What is CVD? CVD stands for cardiovascular disease, which includes heart attacks, strokes, and blocked arteries.
Why does risk matter? A higher “risk” means you’re more likely to develop these conditions over time. Missing sleep or staying up late forces your heart to work harder, raising blood pressure and inflammation.
Your optimal zone: 7–8 hours (lowest long-term risk) + bedtime between 10:00 PM–10:59 PM (aligns with your natural sleep cycle).
All our insights come from large, peer-reviewed studies—so you’re not guessing, you’re sleeping smarter. If you have specific health concerns, be sure to check in with your doctor.
Do you need help with your habit? See our list of international helplines and resources.
The Science Behind It
Sleep duration and timing have profound effects on physical health, cognitive performance, and emotional well-being. SizeMyHabit’s Sleep Calculator translates hours of sleep into cardiovascular risk, metabolic impact, and cognitive outcomes—drawing on chronobiology, epidemiology, and neurobiology.
1. U-Shaped Mortality Curve
Epidemiological studies show a U-shaped association between sleep duration and mortality: both short (<6 h) and long (>9 h) sleepers have increased all-cause mortality risks compared to those with 7–8 h/night. The calculator frames your sleep hours within this optimal window to guide healthy targets.
2. Cardiometabolic Health
Short sleep impairs glucose metabolism: one week of 4 h/night increases insulin resistance by 30% and reduces glucose tolerance comparable to a prediabetic state. Conversely, oversleeping often reflects underlying conditions like sleep apnea, which also elevates cardiovascular risk.
3. Neurocognitive Performance
Sleep is critical for memory consolidation. Slow-wave sleep (<1 Hz EEG) facilitates hippocampal-to-neocortical transfer of declarative memories. Restricting sleep to 5 h/night for three nights reduces next-day cognitive throughput by 30%—equivalent to a blood-alcohol concentration of 0.05%.
4. Circadian Alignment & Social Jetlag
Discrepancies between biological clock and social schedule (“social jetlag”) exceeding 2 h are linked to higher BMI and metabolic syndrome. By capturing bedtime and wake-time, the calculator can quantify social jetlag and recommend adjustments to stabilize circadian rhythms.
5. Behavioral Interventions
Sleep hygiene practices—consistent sleep schedules, limiting screen exposure before bed, and optimizing bedroom environment—improve sleep efficiency by 10–15% in clinical trials. SizeMyHabit integrates these tips and tracks adherence, reinforcing positive routines through self-monitoring.
Sources:
- Kripke, D. F. et al. “Mortality Associated With Sleep Duration.” Sleep (2002)
- Spiegel, K. et al. “Sleep Curtailment in Healthy Young Men.” PNAS (2015)
- Goel, N. et al. “Cognitive Deficits Following Sleep Restriction.” Journal of Sleep Research (2016)
- Wittmann, M. et al. “Social Jetlag: Misalignment of Biological and Social Time.” International Journal of Epidemiology (2011)
- American Academy of Sleep Medicine. “Sleep Hygiene.” (2020)
Disclaimer: This calculator provides estimations based on general population studies and is for informational and educational purposes only. It is not medical advice. Individual health risks can vary. Consult with a healthcare professional for personalized advice regarding your sleep and health.