Health & fitness · free calculator
Sleep debt tracker
Calculate weekly sleep debt vs target and project the make-up time needed at extended nightly sleep.
Weekly sleep debt (hours)
vs target
Show the work
- Weekly total slept50.5
- Weekly target56.0
- Average nightly7.21
- Nights at recovery rate to repay debt5.5
Sleep debt — the metric that actually predicts performance
Sleep debt is cumulative hours short of your target across a rolling window. Unlike "hours slept last night," sleep debt tracks the carryover that determines next-day cognition, mood, and recovery.
Real-world impact of sleep debt
- 2 hours below target one night: ~10% drop in reaction time the next day. Equivalent to ~0.05% blood alcohol.
- 6 hours nightly for a week (when you need 8): -25% executive function, immune suppression, glucose tolerance reduction comparable to pre-diabetes.
- >4 hours weekly debt: athletes show ~5% drop in max strength and 10% drop in time-to-exhaustion.
How to repay sleep debt
You can repay debt, but slowly:
- +1 hour/night for the count of debt-hours you owe is the realistic max
- Sleeping 12 hours one night doesn't undo a week of 6-hour nights
- Weekend "catch-up" is real but partial — studies show full recovery takes 3-4 nights at +1 hour, not one big night
Caveats
The 8-hour target is the median; individual range is 7-9 hours. Some genuine "short sleepers" function at 6 (rare, genetic — DEC2 mutation). Most people who think they only need 6 are actually running with chronic debt and don't notice the impairment.
Track your sleep for 14 days and find your best-feeling 7-day average. That's your real target.
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