Sleep Debt Calculator

What the number means

This tool measures a simple difference between your sleep and a chosen target. If your target is 8 hours and you slept 6 hours, that night contributes 2 hours to the seven-day shortfall. The result does not measure your biological sleep need, sleep quality, or impairment. A night above your target appears in the average but does not mathematically erase a night below it.

The age ranges are a starting point. The CDC sleep-duration guidance says most adults need at least seven hours, while needs vary by age and individual. Set a target within the range shown for your age group, and use actual sleep time rather than time spent in bed.

Can you catch up on lost sleep?

Additional sleep can help after short nights, but there is no reliable one-hour-lost to one-hour-repaid schedule. After repeated short nights, recovery may take several nights. The NIH explains sleep debt, and an NIH review of a weekend catch-up study found that weekend recovery sleep did not reverse all measured effects of weekday sleep restriction in that study. Give yourself adequate sleep opportunity on a regular basis.

If you are trying to make more room for sleep, use our bedtime calculator to compare possible bedtimes. If your schedule keeps drifting, see our practical sleep-schedule reset plan.