Sleep calculator / Sleep debt calculator
Sleep Debt Calculator
Enter how much you slept each night this week. See how much sleep you owe and how to pay it back without wrecking your schedule.
- 100% free
- No sign-up
- No app
Most adults need 7 to 9 hours. Not sure? Use 8.
What is sleep debt?
Sleep debt is the gap between the sleep you need and the sleep you actually get. Sleep an hour short for five nights, and you're five hours in debt by Friday. It builds quietly: people who are chronically short on sleep often stop noticing how tired they are, even though focus, mood and reaction time keep slipping.
Can you pay it back?
Partly. A few nights of extra sleep can bring back alertness after a short run of bad nights. But research suggests weekend lie-ins don't fully undo a week of short sleep. In one study, people who slept short on weekdays and caught up on weekends still showed the same metabolic effects as people who never caught up.
So the best plan has two parts: pay back recent debt gradually, and stop running up new debt.
How to pay back sleep debt
- Go to bed earlier, not up later. An extra 30 to 60 minutes at the start of the night keeps your wake-up time steady, which protects your body clock.
- Spread it out. An extra hour a night over a week beats a 12-hour Saturday.
- Use short naps if you need them. The nap calculator gives you the right alarm time.
- Time your bedtime to your cycles with the sleep calculator.
Not sure you're short on sleep at all? Take the 10-question sleep deprivation quiz.
Frequently asked questions
How much sleep debt is too much?
Anything over a few hours a week is worth fixing. Being short by more than a full night (7+ hours) in a week usually shows up in concentration, mood and driving safety.
Can I catch up on sleep on the weekend?
A little, but it does not fully reverse a week of short nights, and long lie-ins shift your body clock, which can make Sunday night and Monday morning harder. Going to bed earlier works better.
How long does it take to recover from sleep debt?
For a few hours of debt, a few nights with an extra 30 to 60 minutes of sleep is usually enough. Longer-term sleep loss takes longer to recover from.
Sources
Related reading
- Can Your Body Adapt to Less Sleep? What Adapts, What Doesn'tNot really. You get used to feeling tired, but in lab studies performance kept falling on short sleep. What adapts, what doesn't, and how to tell if you're short.4 min read
- Is 5.5 Hours of Sleep Enough? The Mid-Cycle Problem and the Weekly CostNo, not for adults. 5.5 hours is 1.5 hours under the 7-hour minimum and ends mid-cycle. What 4.5 or 6 hours would feel like instead, and a plan to fix it.5 min read
- Is 6.5 Hours of Sleep Enough? The Cycle Math and the Weekly ShortfallFor most adults, no: 6.5 hours is 30 minutes under the 7-hour minimum, and your alarm lands mid-cycle. Here's what it costs per week and how to fix it.5 min read
More free sleep tools
All completely free, no sign-up.
- Sleep CalculatorBest bedtime or wake-up time, based on 90-minute sleep cycles.
- Hours of Sleep CalculatorHow many hours of sleep you will get between bedtime and your alarm.
- Nap CalculatorWhen to set your alarm for a power nap or a full-cycle nap.
- Caffeine Cutoff CalculatorHow much caffeine is still in you at bedtime, and your latest cup.
- Sleep Needs by AgeRecommended hours for every age, from newborns to over-65s.
- Sleep Efficiency CalculatorWhat share of your time in bed you actually spend asleep.
- Shift Work Sleep CalculatorWhen to sleep and stop caffeine around any shift, including nights.
- Kids Bedtime CalculatorThe right bedtime for your child's exact age and wake-up time.
- Chronotype CalculatorNight owl or early bird? Find your chronotype and social jet lag.
- Daylight Saving Time Sleep PlannerA day-by-day plan to shift your sleep before the clocks change.
- Sleep Schedule MakerA full daily timeline from your wake-up time: light, coffee, dinner, wind-down.
- Caffeine Limit CalculatorHow much caffeine you can have today, and how much is left.
- Sleep Deprivation QuizTen quick questions to see if you are running short on sleep.
- Jet Lag CalculatorDays to adjust, plus a shift-before-you-fly schedule.
These results are general estimates, not medical advice. Everyone's sleep is a little different. If you're often exhausted despite enough time in bed, snore loudly, or have been told you stop breathing in your sleep, see a doctor.