Sleep Cycle Calculator Sleep debt calculator
Log your last 7 nights of sleep against your nightly target to see your cumulative sleep debt and roughly how long it takes to pay it back.
4.5 hours behind
Over the last 7 nights you slept 48.5 hours against a target of 56 hours.
What sleep debt actually is
Sleep debt is the running gap between how much sleep you have actually gotten and how much your body needed over the same stretch of nights. It is cumulative: missing 90 minutes one night and 30 minutes the next is not two separate small problems, it is one 2-hour debt your body is still carrying. Unlike a single bad night, which most people recover from quickly, a debt built up over a week or more tends to need more than one long sleep to clear.
- Set your nightly target (most adults: 7 to 9 hours).
- Log what you actually slept each of the last 7 nights.
- The calculator sums the gap between target and actual across the week.
- A rough payback estimate shows how many extra hours of sleep, spread over the nights ahead, would clear it.
Plan tonight’s sleep: calculate your bedtime or wake-up time →
Frequently asked questions
Subtract the hours you actually slept from your nightly target for each of the last several nights, then add up the differences. For example, a 7.5-hour target with nights of 6, 7, 6.5, 8, 7, 6, and 7.5 hours gives a weekly total of 48 hours against a 52.5-hour target, for a 4.5-hour debt.
Mostly, yes, though it takes consistency rather than one marathon night. Sleeping an extra 1 to 2 hours a night over several nights, plus prioritizing a regular schedule, tends to resolve short-term debt. Debt built up over months is harder to fully undo with a few long nights alone.
It helps but rarely clears it completely. The body can only extend normal sleep by so much in a single night, so a large debt built up over a week usually needs several nights of slightly longer, more consistent sleep rather than one 12-hour catch-up night.
Common signs include needing an alarm to wake up, feeling groggy well past getting up, craving caffeine earlier in the day, falling asleep quickly or unintentionally during quiet moments, and noticeably sharper focus or mood on days you happen to sleep in.
Not exactly. Tiredness is how you feel in the moment and can come from many things. Sleep debt is a specific, measurable gap between sleep needed and sleep gotten, built up over days, and it is one of the most common underlying causes of ongoing tiredness.