How the sleep debt calculator works
Sleep debt is the gap between the sleep you need and the sleep you actually get. The calculator adds up your seven nights, multiplies your nightly target by seven, and shows the difference as your estimated shortfall.
Your target is limited to the recommended range for your age group, for example 7–9 hours for adults aged 26–64, and can be set in half-hour steps. Enter each night in hours; use decimals for part hours, such as 6.5 for six and a half hours or 7.25 for seven and a quarter.
Worked example: an 8-hour target
| Night | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|
| Slept | 7 | 6.5 | 6 | 7.5 | 5.5 | 8 | 6.5 |
| Gap | −1 | −1.5 | −2 | −0.5 | −2.5 | 0 | −1.5 |
The nights add up to 47 hours. An 8-hour target over seven nights is 56 hours, so the estimated shortfall is 9 hours, an average of about 1.3 hours a night.
Catching up on lost sleep
A shortfall doesn’t need to be repaid hour for hour. One long lie-in is unlikely to make up for a whole week of short nights, and big swings in your schedule can upset your body clock.
A steadier approach is to move your bedtime a little earlier for several nights and keep your wake-up time consistent. The bedtime calculator can help you pick a time.
When to seek help
Talk to a doctor or a sleep specialist if you:
- have a shortfall most weeks even though you give yourself enough time in bed;
- regularly take longer than 30 minutes to fall asleep, or wake often in the night;
- feel very sleepy during the day, especially while driving or working;
- snore loudly or have been told you stop breathing while asleep.
Frequently asked questions
What counts as a night’s sleep?
Enter the time you were actually asleep, not the time spent in bed. If you’re not sure, estimate: subtract roughly how long it took you to fall asleep and any long wake-ups.
Why can’t I set a target outside the range?
The target is kept within the recommended range for the selected age group so the estimate stays realistic. Change the age group if it doesn’t match you.
Does a shortfall of a few hours matter?
An occasional short night is common. A shortfall that builds up week after week is more likely to affect mood, focus and health, so it’s worth adjusting your routine.
Can I include naps?
Yes. If you nap, add that time to the matching day’s total to get a fuller picture.
Related calculators
Bedtime calculator
Know when you need to wake up? Find the bedtimes that let you wake between sleep cycles.
Wake-up time calculator
Going to bed now or at a set time? Find wake-up times that land at the end of a cycle.
Nap calculator
Plan a 10-, 20- or 90-minute nap and see when to set your alarm.
Sleep needs by age
See the recommended hours of sleep for any age, from newborns to older adults.
Sources
- National Heart, Lung, and Blood Institute. Sleep Deprivation and Deficiency.
- Hirshkowitz M, et al. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health, 2015;1(1):40–43. doi:10.1016/j.sleh.2014.12.010.
- Watson NF, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Journal of Clinical Sleep Medicine, 2015;11(6):591–592. doi:10.5664/jcsm.4758.
- Centers for Disease Control and Prevention. About Sleep.