Sleep debt calculator
Sleep debt is the gap between what you need and what you actually slept. It accumulates day by day and one long weekend night does not clear it: recovery runs at one or two extra hours a night at most.
Catching up restores alertness, but some effects of chronic restriction — on metabolism and mood — are not fully undone by weekend sleep. A debt that rebuilds every week is a scheduling problem, not a recovery problem.
Frequently asked questions
Can I repay it all at the weekend?
Partly. Two long nights clear the acute fatigue but also shift your circadian rhythm, which makes Monday morning worse. A small nightly surplus works better.
How do I know how many hours I need?
On holiday, with no alarm, after three or four recovery days, the time you wake by yourself shows your real need.
Do naps count?
Yes, a twenty to thirty minute nap counts towards the total, though it does not replace full night cycles.