Calculator
Sleep Debt Calculator
Sleep debt accumulates but doesn't repay linearly. Sleeping 12 hours after a bad week doesn't reset you. Enter your past seven nights and your personal sleep need — we'll show the gap and a realistic recovery timeline.
If unknown, see the Sleep Need Estimator.
Quick set
Hours slept each night (most recent first)
Estimated sleep debt
7.0h
Average: 7.0h/night · Target: 8h × 7 = 56h.
Recovery estimate
6 nights
Adding ~1.25h above your need per night.
Caveat
You can't binge-recover. Trying to sleep 12+ hours in one night disrupts your rhythm and yields less recovery than spreading the catch-up across 3–4 nights.
How it works
Sleep debt is simply the difference between the sleep you got and the sleep you needed, accumulated over a window. The calculation is trivial; the recovery model is where most calculators get it wrong.
Lab studies of recovery sleep (Kitamura et al, 2016; Pejovic et al, 2013) consistently show that catch-up sleep is sub-linear: you can't fully recover from a four-hour debt with one extra hour. We use a pragmatic assumption that recovery nights can repay roughly 1.25 hours of debt above your normal need.
Crucially, the underlying physiological recovery is faster for some sleep functions (deep sleep returns within 1–2 nights) and slower for others (full cognitive recovery from a two-week deficit takes longer).
Why it matters
People consistently underestimate their accumulated debt because subjective tiredness adapts within a few days. Van Dongen's landmark 2003 study showed people sleeping six hours a night developed deficits equivalent to total sleep deprivation — and reported feeling “only slightly tired”. The numbers don't lie; your feelings can.
Sources
- 1Van Dongen, H. P. et al.. Effects of cumulative sleep restriction on cognitive performance · Sleep · 2003PMID 12683469
- 2Kitamura, S. et al.. Estimating individual optimal sleep duration and potential sleep debt · Scientific Reports · 2016PMID 27708388