Sleep debt calculator
Log the last 7–14 nights and this calculator totals what you owe against your age-banded sleep need — an hour short on five weeknights is 5 hours of debt — then builds a recovery plan that repays it gradually, because the recovery-sleep research is clear that one catch-up weekend doesn't settle the account.
Sets your target: 8 h/night.
−1 h
−1 h 30 m
−30 m
−2 h
−1 h
+30 m
+1 h
Current debt
4 h 30 m
owed against 8 h × 7 nights
Nights under target
5 / 7
avg −39 m per night
Worst night
2 h
Night 4
Recovery plan
Repay with 20 m earlier to bed on weeknights plus a 1 h 30 m longer lie-in at weekends — about 4 h 40 m a week, clearing in roughly 7 nights.
the arithmetic · 4 h 30 m ÷ (20 m × 5 weeknights + 1 h 30 m × 2 weekend days) ≈ 1 week
Planning tool, not medical advice. These figures are population averages for scheduling your sleep — they don't diagnose or treat any condition. See a clinician for persistent sleep problems.
What is sleep debt, actually?
Sleep debt is the running difference between the sleep your biology needs and the sleep you took. It accumulates nightly and — this is the part most advice misses — it is signed: a long weekend night pays a little back, a short Tuesday adds a little on. The concept is a bookkeeping model, not a measured quantity, but it tracks something real: the homeostatic sleep pressure that builds the longer you go under-slept and only fully discharges with sustained adequate sleep.
Why is the recovery plan deliberately boring?
Because the dramatic version doesn't work. Recovery studies show the body repays debt by deepening sleep (more slow-wave and REM per hour) across several nights, not by accepting one 12-hour marathon. The plan above adds 15–60 minutes to weeknights and a longer lie-in at weekends — the tolerated upper band — and tells you roughly how many weeks the repayment takes. A debt over ~14 hours is flagged as chronic, because at that size the first question isn't repayment, it's where the hours are leaking.
How do you stop debt at the source?
Debt has two causes: not enough time in bed, or time in bed that isn't becoming sleep. The first is a scheduling problem — the bedtime calculator fixes it in one arithmetic step. The second is an efficiency problem — if you're in bed 8 hours but asleep 6.5, measure that with the sleep efficiency calculator and tighten the window rather than extending it.
FAQ
Can you really repay sleep debt?
Partly, and gradually. The deep-sleep rebound is real — recovery nights contain extra slow-wave sleep — but the research (Banks & Dinges 2007 and successors) shows full recovery from even a week of restriction takes more than a week, and some performance deficits in the studies did not fully recover after three nights of 10-hour recovery sleep. Repay it slowly and stop creating it; do not bank on one heroic weekend.
Can I catch up on sleep at the weekend?
A modest weekend lie-in (60–90 minutes) takes the edge off a weekday debt and is better than nothing. A 3-hour Saturday binge does not repay 3 hours of debt cleanly — it fragments the following night's sleep and drifts your circadian clock, which is what makes Monday feel like jet lag. Consistency repays debt better than volume.
How is sleep debt calculated?
Night by night: your sleep need (from your age band) minus the hours you actually slept, summed. Sleep 7 h against an 8 h need and you owe 60 minutes; sleep 9.5 h on Saturday and you repay 90. The calculator keeps the ledger signed, because oversleeping genuinely pays a little back.
What are the symptoms of sleep debt?
The early ones are subtle: afternoon energy crashes, reliance on caffeine to feel normal, falling asleep within 5 minutes of your head hitting the pillow (healthy latency is 10–20 minutes), and weekend oversleep of more than an hour. The late ones — low mood, poor focus, getting every cold that passes — are why this is worth calculating rather than guessing.
How we source this
The sleep-duration figures come from the National Sleep Foundation's 2015 consensus panel (Hirshkowitz et al., Sleep Health) — 18 experts convened from 12 stakeholder organisations, reviewing 300+ studies. The cycle, REM, jet-lag and wind-down models are built from the primary literature, and every source is listed with its context on the methodology & sources page.
Content is written and maintained by the SleepMaxx Calculator editorial team and checked against those sources. This site is not medically reviewed— no clinician reviews this content, and we would rather say that in plain text than hang a reviewer byline we don't have. These are planning tools built on population averages; for a personal sleep problem, a clinician is the right next step.
You will also not find an Epworth Sleepiness Scale, a STOP-BANG questionnaire or an AHI estimator here. Those are clinical screening instruments: their scores only mean something in the hands of someone who can act on them, and hosting them on a calculator site is a safety problem, not a feature. We exclude them deliberately.
Keep planning
Wind-Down Routine Planner
Your pre-bed schedule worked backwards from bedtime — chronotype-shaped, scaled to the time you have. Printable.
Sleep Schedule Calculator
A full week of bedtimes and alarms — including shift-work anchor schedules.
Sleep Cycle Calculator
Bedtimes from a wake time, alarms from a bedtime — cycle length and latency as dials, not settings.
Bedtime Calculator
Enter your wake time — get the bedtimes that land you at the end of a sleep cycle.