Sleep Debt Calculator
Calculate how much sleep debt you've built up over the last 7 nights, compared to how much sleep you actually need.
How to use the calculator
- Enter how many hours of sleep you need per night.
- Enter how many hours you've actually slept over the last 7 nights.
- See your total accumulated sleep debt.
How it's calculated
Nights with MORE sleep than recommended don't count as a "surplus" that offsets the debt — sleep research suggests sleep debt can't simply be "banked" or fully repaid with one good night, even though a good night does help short-term functioning.
Can sleep debt be repaid?
Partly. The body compensates for short-term sleep loss fairly effectively: after a few nights of too little sleep, the proportion of deep sleep increases when you finally do sleep in, as though the system prioritises the most restorative stage first. A single long night or a quiet weekend therefore recovers much of a deficit built up over a few days.
Chronic debt behaves differently. If you go months systematically short of sleep, the account cannot be settled with one good night, and research suggests some of the effect on attention and reaction time persists even after you subjectively feel rested. Regularity — going to bed and getting up at roughly the same time — therefore does more than alternating between short nights and long weekends.
Frequently asked questions
Can I "catch up" on sleep debt over the weekend?
Partially — extra weekend sleep can improve how you feel, but research suggests it doesn't fully reverse the cognitive effects of prolonged sleep debt.
Why don't nights with lots of sleep count as a subtraction?
Because sleep debt behaves asymmetrically in practice — the body builds up debt faster than it pays it down, even with good sleep afterward.
How much sleep do adults actually need?
Most adults need 7-9 hours per night, though it varies individually. See the sleep needs calculator for a more detailed assessment.