Free Tool
Sleep Debt Calculator
Enter how many hours you slept each night this week. We'll calculate your sleep debt and what it means for your body.
What is sleep debt?
Sleep debt is the cumulative deficit that builds when you consistently sleep less than your body needs. Most adults require 7–9 hours per night. If you sleep 6 hours when your body needs 8, you accumulate 2 hours of sleep debt that night. Do that for a week and you're carrying 14 hours of deficit.
Sleep debt isn't just tiredness. Research from the University of Pennsylvania shows that people with chronic sleep restriction — as little as 6 hours per night for two weeks — perform as poorly on cognitive tests as people who have been awake for 24 hours straight. Crucially, they don't perceive themselves as impaired.
Short-term sleep debt (1–2 nights) is largely recoverable with extra sleep the following nights. Chronic sleep debt — built up over weeks or months — is harder to reverse and is associated with increased risk of cardiovascular disease, impaired glucose metabolism, weakened immune function, and mood dysregulation.
Hours slept each night
This tool is for informational purposes only and is not medical advice.
Understanding your results
0–2 hours — Well rested
Your sleep patterns are healthy. Minor fluctuations are normal. Focus on maintaining consistency.
3–7 hours — Moderate deficit
You're carrying meaningful debt. Cognitive performance and mood are likely impacted. Prioritise recovery sleep over the next 1–2 weeks.
8–14 hours — Significant deficit
This level of debt produces measurable impairments in reaction time, decision-making, and emotional regulation. Structural changes to your schedule are needed.
15+ hours — Chronic deficit
This level of cumulative restriction carries real health risk. If this reflects a consistent pattern, it's worth examining root causes — stress, schedule, or an undiagnosed sleep disorder.
How to recover
You cannot fully repay sleep debt in a single weekend. Research suggests the most effective recovery is gradual: aim for 30–60 extra minutes per night over several days rather than one very long sleep session, which can disrupt your circadian rhythm.
The most important long-term fix is raising your baseline: a consistent bed time, a consistent wake time, and protecting sleep from encroachment by screens, late meals, and caffeine. Small consistent gains compound faster than occasional catch-up sessions.
For a deeper guide: Sleep Debt: What It Is and How to Recover →
This tool is for informational purposes only and does not constitute medical advice. If you experience persistent excessive daytime sleepiness, consult a healthcare professional to rule out sleep disorders such as sleep apnoea.