Sleep debt calculator
Type how long you actually slept each night this week and choose your nightly target. You will see how far short you fell, night by night, and an honest note on what that number can and cannot tell you.
Your week
Showing a sample week. Type your own hours over it.
- Short of target
- 9 h
- Average a night
- 6 h 56 min
- Nights under target
- 5 of 7
- Week overall
- 7 h 30 min behind
- Slept
- Short of target
- Target: 8 h
A large shortfall: more than a whole night's sleep below your target across the week. Your longer nights added back 1 h 30 min, which the research below suggests is not a full repayment. 5 nights were under the 7 hours recommended for adults.
Not medical advice. This is arithmetic, not a measure of your health. If you sleep enough but still feel very sleepy in the day, or you snore loudly, see a doctor.
What the numbers mean
Short of target adds up only the nights that fell below your target. Week overall subtracts everything you slept from seven times your target, so long nights count against short ones. The difference between the two shows how much a lie-in is doing the heavy lifting. Use real time asleep, not time in bed: a sleep diary makes that easier to estimate.
Why sleep debt is only a rough idea
The body does not keep a tidy ledger. In one lab study, two weeks of 6 hours or less a night built up deficits on attention tests equal to up to two nights with no sleep at all, yet people seemed largely unaware of how impaired they were (Van Dongen et al., 2003). In another, after a week of restricted sleep, three nights of 8 hours in bed did not bring reaction speed back to its starting level (Belenky et al., 2003). And catching up at the weekend did not prevent the changes in insulin sensitivity and evening snacking caused by short weeknights (Depner et al., 2019).
So treat a big number as a nudge towards regular, sufficient sleep, not as a bill to pay off in one go.
Sources
- Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. The cumulative cost of additional wakefulness. Sleep 2003;26(2):117–126. doi:10.1093/sleep/26.2.117
- Belenky G, Wesensten NJ, Thorne DR, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. J Sleep Res 2003;12(1):1–12. doi:10.1046/j.1365-2869.2003.00337.x
- Depner CM, Melanson EL, Eckel RH, et al. Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep. Current Biology 2019;29(6):957–967.e4. doi:10.1016/j.cub.2019.01.069
- Watson NF, Badr MS, Belenky G, et al. Recommended amount of sleep for a healthy adult. Sleep 2015;38(6):843–844. doi:10.5665/sleep.4716
- American Academy of Sleep Medicine. Obstructive sleep apnea.
Questions
What target should I use?
The AASM recommends at least 7 hours for adults; pick the amount after which you wake refreshed without an alarm on holiday. Children and teens need more: see the ages page.
Can I pay back sleep debt at the weekend?
Partly. Extra sleep helps you feel better, but studies found that a weekend lie-in or a few normal nights did not fully undo a week of short sleep. Regular nights work better than big catch-ups.
When should I see a doctor?
If you feel very sleepy in the day despite enough time in bed, snore loudly, gasp or stop breathing in your sleep, or struggle to sleep for weeks, see a doctor. The AASM lists loud snoring and daytime sleepiness as common signs of sleep apnea.