What does this tool do?
Sleep debt is the cumulative gap between the sleep you need and the sleep you get. This calculator multiplies a nightly shortfall by the number of nights and estimates recovery time.
The Formula
Sleep debt (h) = (Target sleep − Average sleep) × NightsFrequently Asked Questions
Can I repay sleep debt on the weekend?
Extra weekend sleep can reduce some effects, but it does not fully reverse them and can shift your body clock. A consistent schedule is more reliable.
How much sleep do adults need?
Most adults need 7–9 hours, though the right amount varies. If you need an alarm to wake and feel groggy most mornings, your target may be too low.