Sleep Debt Calculator

How the debt is calculated

The weekly debt is your target times seven, minus the seven nights you entered, floored at zero — so a 8-hour target against 49 hours slept is a 7-hour debt, and sleeping more than your target does not earn credit. The 30-, 90- and 365-day projections take your average nightly shortfall and repeat it: 45 minutes short a night is 22.5 hours over a month and 274 over a year. That is straight multiplication, which is what makes it a projection of the pattern rather than a measurement of your body.

Two of the numbers on this page are ours and neither has a citation behind it. The cognitive performance figure subtracts 13 percentage points for every hour of average nightly shortfall and stops at 30 per cent — so an hour short reads 87 per cent, two hours 74. That slope is our own construction. The research it gestures at is real and much less tidy: restricting sleep across consecutive nights produces cumulative deficits on attention tasks, and people rate themselves as barely impaired while measuring as substantially impaired. A single percentage of general performance is not something that literature supports, and we would rather say that than pretend the number is a finding.

The recovery estimate is the same kind of figure. It divides your debt by the hours a 9-hour night gives you above your own target, so an 8-hour target recovers one hour a night and a 7-hour target two. Real recovery is not linear like that — the first long night returns more than the fifth — and 9 hours is an assumption we picked as a plausible catch-up night. Read the number as an order of magnitude for how long the hole takes to fill, not as a schedule.

Nothing on this site is medically reviewed. Every figure above was read out of the code that runs on this page, and where a number is our own judgement rather than a published one, the note says so and cites nothing. Method last checked 21 August 2026.