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💤 Sleep Debt Calculator

Track your weekly sleep deficit, Sleep Score & get a science-backed recovery plan

Age Group & Sleep Need
This Week's Sleep Log — Hours Per Night
Mon
6.5h
Tue
6.5h
Wed
7.0h
Thu
6.0h
Fri
7.5h
Sat
8.5h
Sun
8.0h
Recovery Method
Sleep Health Summary
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Sleep Score
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Enter your sleep hours to see your score.
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Weekly sleep debt
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Hrs Debt
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Avg / Night
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Recovery Days
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Goal Met
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Days Below
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Cog. Impact
Estimated Cognitive Impact

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Recommended Bedtime Tonight
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Based on your wake time and recovery need.

Analysis & Tips
This Week: Sleep vs Recommendation
Recovery Scenarios — Days to Clear Your Current Debt
Gradual
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+30 min/night
Standard
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+1 hr/night
Aggressive
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+2 hrs/night
Recovery Days Matrix — Sleep Need × Extra Sleep per Night

Highlighted cell = your current settings. Green = fast recovery, red = slow.

Goal Seeker — Recovery by Date
Enter a target date to calculate your required extra sleep per night.
Bedtime Optimizer

Ideal bedtimes based on 90-min sleep cycles:

Best Nap Strategy for Your Debt

🧠 Sleep Science — Fast Facts

    🌎 Recovery Tips

    • Consistent bedtime matters more than total hours — your circadian clock thrives on regularity.
    • Avoid bright light 1-2 hours before bed. Blue light from screens suppresses melatonin by up to 50%.
    • Keep it cool — core body temperature drops 1-2°F during sleep. A room at 65-68°F (18-20°C) is optimal.
    • Caffeine has a half-life of 5-7 hours — a 3 PM coffee still has half its caffeine at 9 PM.
    How to Use This Calculator
    1

    Enter Your Sleep Log

    Input how many hours you slept each night over the past week. The bars update live to show which nights hit your goal.

    2

    Set Your Sleep Need

    Choose your age group or enter a custom recommended hours value. Most adults need 7-9 hours.

    3

    See Your Sleep Score

    Your 0-100 Sleep Score summarizes your week at a glance — like a credit score for sleep health.

    4

    Plan Your Recovery

    Switch to the Recovery Planner tab to find your optimal bedtime, nap strategy, and a goal-seeker for target recovery dates.

    Formulas & Methodology
    Daily Deficit
    max(0, Required - Actual)
    Hours lost per night vs your personal sleep need.
    Net Weekly Debt
    max(0, ΣDeficits - ΣSurplus)
    Total debt minus nights you slept over your target.
    Sleep Score
    100 - debt×8 - daysBelow×2
    Combines debt severity and consistency, clamped 0-100.
    Cognitive Impact
    min(40%, debt × 4%)
    Estimated performance reduction based on sleep restriction research.

    About this calculation · Accuracy & Methodology

    Frequently Asked Questions
    How is the Sleep Score calculated?

    The Sleep Score (0-100) uses the formula: 100 minus (net debt hours × 8) minus (days below recommendation × 2), clamped between 0 and 100. It rewards both low debt and consistency — you can't compensate for 5 bad nights with 2 good ones. A score of 90+ is Excellent; 70-89 Good; 50-69 Fair; below 50 indicates significant sleep deprivation.

    How accurate is the cognitive impairment estimate?

    The estimate (approximately 4% per hour of debt, capped at 40%) is simplified from sleep restriction research. Real impairment is non-linear — reaction time degrades faster than vocabulary recall. Individual genetic sensitivity also varies significantly (some people are "short sleepers" who function well on 6 hours). The estimate is directionally useful but not a clinical measurement.

    Can you fully recover from chronic sleep debt?

    Acute sleep debt (days to a week) largely recovers with 3-4 nights of adequate sleep. Chronic deprivation spanning months or years has more lasting effects — some metabolic and epigenetic changes from long-term sleep restriction appear only partially reversible. This is why consistently adequate sleep is far more protective than periodic recovery.

    Do naps count toward repaying debt?

    Yes, but with diminishing efficiency. A 90-minute nap with REM sleep is roughly 60-70% as restorative as an equivalent overnight sleep duration — because daytime naps occur outside the body's optimal circadian sleep window. A 20-minute power nap improves alertness for 2-3 hours without meaningful circadian disruption and without causing sleep inertia (grogginess).

    What is social jet lag?

    Social jet lag refers to the difference between your biological clock's preferred sleep timing and your actual social schedule. If your body wants to sleep at 11 PM but work forces a 6 AM wake-up, you accumulate debt on weekdays and try to repay on weekends by sleeping until 9-10 AM — effectively flying 2 time zones east every Monday. Each hour of social jet lag is associated with a 33% higher risk of obesity and elevated cardiovascular risk markers.

    Why is 90 minutes the ideal nap length?

    A complete human sleep cycle takes approximately 90 minutes, progressing through light sleep, deep slow-wave sleep, and REM sleep. Waking at the end of a cycle — rather than mid-cycle during deep sleep — minimizes sleep inertia (post-nap grogginess) and maximizes the cognitive benefit of the nap. A 90-minute nap should be timed to end by 3 PM to avoid disrupting nighttime sleep.

    How does sleep debt affect weight and metabolism?

    Sleep deprivation raises ghrelin (hunger hormone) by up to 28% and reduces leptin (satiety hormone) by 18%, creating powerful cravings for calorie-dense foods. Just two weeks of mild sleep restriction (6 hours/night) impairs insulin sensitivity equivalently to prediabetes. Chronically sleep-deprived individuals burn fewer calories at rest and store more as fat due to elevated cortisol.

    When is the best time to take a nap?

    The optimal nap window is 1-3 PM, aligned with the natural post-lunch circadian dip in alertness. Napping after 3 PM delays sleep pressure and can make it harder to fall asleep at night. For a 20-minute power nap, set an alarm for 25-30 minutes to allow time to fall asleep. For a 90-minute cycle nap, time it to end by 2:30-3 PM.

    Key Terms
    Sleep Debt
    The cumulative deficit when actual sleep falls short of your biological need. Builds over days and cannot be fully repaid in a single weekend.
    Sleep Score
    A 0-100 composite index combining your weekly debt, consistency, and average hours. 90+ = Excellent, 70-89 = Good, 50-69 = Fair, <50 = Poor.
    Basal Sleep Need
    The amount of sleep your body genetically requires per night for optimal functioning — not what you think you can manage.
    Social Jet Lag
    The circadian disruption caused by sleeping late on weekends and early on weekdays — equivalent to traveling 1-2 time zones every week.
    Sleep Inertia
    Grogginess and impaired performance for 15-60 minutes after waking from deep (slow-wave) sleep. Worst when woken mid-cycle.
    Microsleep
    Involuntary 1-15 second episodes of sleep that occur during severe deprivation, often unnoticed. A primary cause of drowsy driving accidents.
    Real-World Examples
    Mild Debt

    The Late-Night Worker

    Sleep log: 7 hrs Mon-Fri, 9 hrs Sat-Sun. Recommended: 8 hrs.

    Debt: 5 hrs (Mon-Fri shortfall), offset by 2 surplus weekend hours = 3 hrs net.

    Sleep Score ~76. Recovery in 3 nights at +1 hr/night. Mild cognitive drag, easy to fix.

    Moderate Debt

    The New Parent

    Sleep log: Averaging 5.5 hrs/night with constant interruptions. Recommended: 8 hrs.

    Debt: 17.5 hrs across the week. Cognitive impairment ~28%.

    Sleep Score ~26. Takes 9+ nights of +2 hrs to recover. Equivalent to mild legal intoxication daily.

    Zero Debt

    The Consistent Sleeper

    Sleep log: 8 hrs every night. Recommended: 8 hrs.

    Debt: 0 hrs. No deficit on any day.

    Sleep Score 100. Peak cognitive performance. Immune function, metabolism, and mood all optimal.

    Understanding & Recovering from Sleep Debt

    Sleep Debt Is a Real, Measurable Deficit

    Losing just 1 hour of sleep per night for a week causes measurable declines in reaction time, decision-making accuracy, and emotional regulation — equivalent to two full nights of total sleep deprivation. The cruel irony: after a week of 6-hour nights, most people report feeling only mildly sleepy, yet objective tests show performance equal to being legally drunk.

    You Cannot Sleep-Bank or Weekend-Recover

    Sleeping extra before a deprived period provides minimal protection — your brain cannot store sleep in advance. Weekend catch-up (sleeping in 2-3 extra hours Saturday and Sunday) partially repays acute debt but disrupts your circadian rhythm, creating "social jet lag" that makes Monday mornings perpetually harder. Worse, the metabolic damage from a week of short sleep — elevated cortisol, impaired insulin sensitivity, increased ghrelin — may not fully reverse even after three nights of recovery sleep.

    How Recovery Actually Works

    Research from the University of Pennsylvania's sleep lab shows that full cognitive recovery from one week of 6-hour nights takes approximately 3-4 days of adequate (8+ hour) sleep. The most efficient approach: extend sleep by a consistent 30-60 minutes earlier bedtime each night rather than large weekend catch-ups. Naps help — a 90-minute early-afternoon nap containing a full REM cycle can repay 60-70% of an equivalent overnight debt hour.

    The Long-Term Cost of Chronic Deprivation

    Emerging research suggests that months or years of short sleep produce epigenetic changes in immune and metabolic genes that may not be fully reversible. Consistently sleeping under 6 hours is associated with a 48% elevated risk of heart disease, 36% increased risk of colorectal cancer, and a near-doubling of Alzheimer's-related beta-amyloid plaque accumulation. Sleep is not a lifestyle preference — it is essential biological maintenance.