What it is for
"Sleep debt" is the accumulated gap between how much sleep you need and how much you actually got. This calculator does that math for the past week: you enter the hours you need per night and the hours slept on each of the last 7 nights.
Formula
net debt = sum(needed − slept) over the 7 nights, which equals needed × 7 − total slept. A positive result is debt; a negative result is a surplus (you slept more than you needed). Nights where you slept extra offset short nights in the net figure. We also show total slept, total needed and the nightly average.
How much sleep do you need?
The National Sleep Foundation (2015) recommends 7 to 9 hours for adults aged 18 to 64 and 7 to 8 hours for those 65 and over; individual needs vary. If you do not know yours, the recommended sleep calculator can be a starting point. A useful practical indicator is how many hours you naturally sleep on vacation without an alarm.
Worked example
A need of 8 h per night (56 h for the week). Nights: 7, 6.5, 7, 8, 5.5, 9 and 8 hours, a total of 51 h. Net debt: 56 − 51 = 5 h, an average of 7 h 17 min per night.
About paying it back
In general, recovery tends to need several nights of regular sleep with a little extra time in bed rather than a single very long night. Everyone responds differently, and many weeks of short sleep are not offset by one weekend.
Limits
The math is purely arithmetic and depends on how accurately you remember your sleep hours. It does not measure sleep quality and does not diagnose anything. If you sleep what you need but have strong daytime sleepiness or other persistent symptoms, talk to a health professional.
Frequently asked questions
What is sleep debt?
It is the accumulated gap between the hours of sleep you need and the hours you actually slept over a period.
Does sleeping in on weekends pay it back?
It helps reduce the balance, but recovery usually takes several regular nights. One weekend does not replace a whole week of short sleep.
How do I find out how much sleep I need?
General recommendations for adults are 7 to 9 hours, but needs vary. Notice how much you naturally sleep when you do not need an alarm.
Does this calculator diagnose anything?
No. It is a simple hours calculation. If you have excessive sleepiness or persistent problems, see a health professional.