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Sleep debt is the gap between the sleep your body needs and the sleep you actually get. It accumulates over days and weeks — and the science is unambiguous: a 2-hour/night deficit for two weeks produces the same cognitive impairment as being awake for 24 hours straight. This calculator totals your weekly sleep debt, estimates how long you need to recover, and shows what a healthier schedule looks like.
The US CDC and UK NHS give very similar age-banded targets (hours per 24h):
"I only need 5 hours" is almost always self-reported and almost always incorrect. Fewer than 1% of people are true short sleepers (carriers of DEC2 and ADRB1 gene variants). The rest of us accumulate debt.
This tool subtracts each night's actual sleep from your target, sums the shortfall over 7 days, and reports:
Partially. Research from Walker (UC Berkeley) and Van Dongen shows that weekend lie-ins help recover some short-term cognitive function but do not reverse the metabolic, immune, and cardiovascular damage from chronic deficit. A single 10-hour sleep won't undo two weeks of 5-hour nights. The only real fix is consistently getting enough sleep.
The CDC lists insufficient sleep (< 7 hours) as a public health problem. Roughly 1 in 3 US adults do not get enough sleep. Consequences include increased risk of obesity, type 2 diabetes, hypertension, depression, and motor-vehicle crashes (drowsy driving is responsible for ~6,000 fatal US crashes per year).
The NHS "Every Mind Matters" service and the Royal Society for Public Health both emphasise 7–9 hours per night. UK adults average about 6.8 hours — around 40% report insufficient sleep. The NHS's Sleepio CBT-I programme is NICE-recommended for persistent insomnia.
A chronic 5+ hours/week deficit correlates with measurable drops in attention, memory, and reaction time. More than 10 hours/week for multiple weeks is associated with elevated risk of cardiovascular disease, metabolic syndrome, and depression.
Short naps (10–20 min) boost alertness without hurting night sleep. Longer naps (60–90 min, one full sleep cycle) can repay some debt but may delay bedtime if taken too late. NASA-style 20-minute power naps are the safest bet.
Regular is better. Erratic schedules — "social jetlag" — are independently linked to obesity and mood disorders. Consistency matters almost as much as total hours.
Regular moderate exercise improves sleep quality and reduces time to fall asleep, but it doesn't remove the need for total hours. Finish vigorous exercise at least 2 hours before bed.
If you regularly sleep 7+ hours and still feel exhausted, have heavy snoring, witnessed pauses in breathing, or persistent insomnia over 3 months — ask your GP or primary-care doctor about sleep apnoea and CBT-I.
This tool estimates sleep debt for informational purposes only and is not a substitute for medical advice or a sleep assessment. Sleep need varies by age, health, work schedule, and sleep disorders. Seek professional guidance if fatigue, insomnia, or excessive daytime sleepiness persists.
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